THE OCEAN WORLD.

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET AND CHARING CROSS.

Plate I.—The Argonaut sailing in the open sea.

THE

OCEAN WORLD:

BEING A DESCRIPTION OF

THE SEA AND ITS LIVING INHABITANTS.

BY

LOUIS FIGUIER.

THE CHAPTERS ON CONCHOLOGY REVISED AND ENLARGED
BY CHARLES O. GROOM-NAPIER, F.G.S., &c.

WITH 427 ILLUSTRATIONS.

LONDON:
CASSELL, PETTER, AND GALPIN;

AND 596, BROADWAY, NEW YORK.

PREFACE.

"Our Planet is surrounded by two great oceans," says Dr. Maury, the eminent American savant: "the one visible, the other invisible; one is under foot, the other over head. One entirely envelopes it, the other covers about two-thirds of its surface." It is proposed in "The Ocean World" to give a brief record of the Natural History of one of those great oceans and its living inhabitants, with as little of the nomenclature of Science, and as few of the repulsive details of Anatomy, as is consistent with clearness of expression; to describe the ocean in its majestic calm and angry agitation; to delineate its inhabitants in their many metamorphoses; the cunning with which they attack or evade their enemies; their instructive industry; their quarrels, their combats, and their loves.

The learned Schleiden eloquently paints the living wonders of the deep: "If we dive into the liquid crystal of the Indian Ocean, the most wondrous enchantments are opened to us, reminding us of the fairy tales of childhood's dreams. The strangely-branching thickets bear living flowers. Dense masses of Meandrineas and Astreas contrast with the leafy, cup-shaped expansions of the Explanarias, and the variously-branching Madrepores, now spread out like fingers, now rising in trunk-like branches, and now displaying an elegant array of interlacing tracery. The colouring surpasses everything; vivid greens alternate with brown and yellow; rich tints, ranging from purple and deepest blue to a pale reddish-brown. Brilliant rose, yellow, or peach-coloured Nullipores overgrow the decaying masses: they themselves being interwoven with the pearl-coloured plates of the Retipores, rivalling the most delicate ivory carvings. Close by wave the yellow and lilac Sea-fans (Gorgonia), perforated like delicate trellis-work. The bright sand of the bottom is covered with a thousand strange forms of sea-urchins and star-fishes. The leaf-like Flustræ and Escharæ adhere like mosses and lichens to the branches of coral—the yellow, green, and purple-striped limpets clinging to their trunks. The sea-anemones expand their crowns of tentacula upon the rugged rocks or on flat sands, looking like beds of variegated ranunculuses, or sparkling like gigantic cactus blossoms, shining with brightest colours.

"Around the branches of the coral shrubs play the humming-birds of the ocean: little fishes sparkling with red or blue metallic glitter, or gleaming in golden green or brightest silvery lustre; like spirits of the deep, the delicate milk-white jelly-fishes float softly through the charmed world. Here gleam the violet and gold-green Isabelle, and the flaming yellow, black, and vermilion-striped Coquette, as they chase their prey; there the band-fish shoots snake-like through the thicket, resembling a silvery ribbon glittering with rose and azure hue. Then come the fabulous cuttle-fishes, in all the diaphanous colours of the rainbow, but with no definite outline.

"When day declines, with the shades of night this fantastic garden is lighted up with renewed splendour. Millions of microscopic medusæ and crustaceans, like so many glowing sparks, dance through the gloom. The Sea-pen waves in a greenish phosphorescent light. Whatever is beautiful or wondrous among fishes, Echinoderms, jelly-fishes and polypi and molluscs, is crowded into the warm and crystal waters of the Tropical ocean."

It is stated on the Title-page that "The Ocean World" is chiefly translated from M. Louis Figuier's two most recent works. In justice to that gentleman, we must explain this statement. The History of the Ocean is to a large extent, but not wholly, compiled from "La Terre et les Mers," one of the volumes of M. Figuier's "Tableau de la Nature;" but the larger portion of the work is a free translation of that author's latest work, "La Vie et les Mœurs des Animaux." Other chapters, such as "Life in the Ocean," the chapter on Crustaceans, and some others, are compiled from various sources; they will not be found in either of M. Figuier's volumes; but in other respects his text has been pretty closely followed.

M. Figuier's plan is to begin the study of animals with the less perfect beings occupying the lower rounds of the Zoological ladder, his reason for doing so being an impression that the presence of the gradually perfecting animal structure, from the simplest organisms up to the more perfect forms, was specially calculated to attract the reader. "What can be more curious or more interesting to the mind," he asks, "than to examine the successive links in the uninterrupted chain of living beings which commence with the Infusoria and terminate in Man?"

The work, he hopes, is not without the impress of a true character of novelty and originality; at least he knows no work in which the strange habits and special interests of the Zoophytes and Molluscs can be studied, nor any work in which an attempt is made to represent them by means of designs at once scientifically correct and attractive from the picturesque character of the illustrations, most of which have been made from specimens selected by Monsieur Ch. Bévalet from the various museums in Paris.

One of those charming plain-speaking children we sometimes meet with lately said to M. Figuier, "They tell me thou art a vulgariser of Science. What is that?"

He took the child in his arms, and carried it to the window, where there was a beautiful rose-tree in blossom, and invited it to pull a rose. The child gathered the perfumed flower, not without pricking itself cruelly with the spines; then, with its little hands still bleeding, it went to distribute roses to others in the room.

"Thou art now a vulgariser," said he to the child; "for thou takest to thyself the thorns, and givest the flowers to others!"

The parallel, although exaggerated, is not without its basis of truth, and was probably suggested by the criticism some of his works have met with; the critics forgetting apparently that these works are an attempt to render scientific subjects popular, and attractive to the general reader.

In the present edition of "The Ocean World" it is only necessary to add to the above (dated January, 1868), that the work has been revised throughout, and some not unimportant errors corrected. For several of these I am indebted to Mr. C. O. G. Napier, who has rearranged the whole of the Mollusca. Mr. David Grieve has kindly revised and added to the Crustacea; and to the Messrs. Johnston of Montrose, and Dr. Wilson Johnston of the Bengal service, I am indebted for some valuable practical information respecting the salmon and the various modes of taking it.

W. S. O.
March 1, 1869.

CONTENTS.

ILLUSTRATIONS.

THE OCEAN WORLD.

CHAPTER I.

THE OCEAN.

Ἄοιστον μὲν ὔδωρ—"The best of all things is water."—Pindar.

It is estimated that the sea covers nearly two-thirds of the surface of the earth. The calculation, as given by astronomers, is as follows: The surface of the earth is 31,625,625½ square miles, that portion occupied by the waters being about 23,814,121 square miles, and that consisting of continents, peninsulas, and islands, being 7,811,504 miles; whence it follows that the surface covered with water is to dry land as 3·8 is to 1·2. The waters thus cover a little more than seven-tenths of the whole surface. "On the surface of the globe," Michelet remarks, "water is the rule, dry land the exception."

Nevertheless, the immensity and depth of the seas are aids rather than obstacles to the intercourse and commerce of nations; the maritime routes are now traversed by ships and steamers conveying cargoes and passengers equal in extent to the land routes. One of the features most characteristic of the ocean is its continuity; for, with the exception of inland seas, such as the Caspian, the Dead Sea, and some others, the ocean is one and indivisible. As the poet says, "it embraces the whole earth with an uninterrupted wave."

Περὶ πᾶσαν θ' εἱλισσομένου

χθόν' ἀκοιμἡτω ῥεύματι.

Æschylus in Prometheus Vinctus.

The mean depth of the sea is not very exactly ascertained, but certain phenomena observed in the movement of tides are supposed to be incapable of explanation without admitting a mean depth of three thousand five hundred fathoms. It is true that a great number of deep-sea soundings fall short of that limit; but, on the other hand, many others reach seven or eight thousand. Admitting that three thousand fathoms represents the mean depth of the ocean, Sir John Herschel finds that the volume of its waters would exceed three thousand two hundred and seventy-nine million cubic yards.

This vast volume of water is divided by geographers into five great oceans: the Arctic, the Atlantic, Indian, Pacific, and Antarctic Oceans.

The Arctic Ocean extends from the Pole to the Polar Circle; it is situated between Asia, Europe, and America.

The Atlantic Ocean commences at the Polar Circle and reaches Cape Horn. It is situated between America, Europe, and Africa, a length of about nine thousand miles, with a mean breadth of two thousand seven hundred, covering a surface of about twenty-five million square miles, placed between the Old World and the New. Beyond the Cape of Storms, as Cape Horn may be truly called, it is only separated by an imaginary line from the vast seas of the south, in which the waves, which are the principal source of tides, have their birth. Here, according to Maury, the young tidal wave, rising in the circumpolar seas of the south, and obedient to the sun and moon, rolls on to the Atlantic, and in twelve hours after passing the parallel of Cape Horn is found pouring its flood into the Bay of Fundy, whence it is projected in great waves across the Atlantic and round the globe, sweeping along its shores and penetrating its gulfs and estuaries, rising and falling in the open sea two or three feet, but along the shore having a range of ten or twelve feet. Sometimes, as at Fundy on the American coast; at Brest on the French coast; and Milford Haven, and the mouth of the Severn in the Bristol Channel, rising and falling thirty or forty feet, "impetuously rushing against the shores, but gently stopping at a given line, and flowing back to its place when the word goes forth, 'Thus far shalt thou go, and no farther.' That which no human power can repel, returns at its appointed time so regularly and surely, that the hour of its approach and the measure of its mass may be predicted with unerring certainty centuries beforehand."

The Indian Ocean is bounded on the north by Asia, on the west by Africa, on the east by the peninsula of Molucca, the Sunda Isles, and Australia.

The Pacific, or Great Ocean, stretches from north to south, from the Arctic to the Antarctic Circle, being bounded on one side by Asia, the island of Sunda, and Australia; on the other by the west coast of America. This ocean contrasts in a striking manner with the Atlantic: the one has its greatest length from north to south, the other from east to west; the currents of the Pacific are broad and slow, those of the other narrow and rapid; the waves of this are low, those of the other very high. If we represent the volume of water which falls into the Pacific by one, that received by the Atlantic will be represented by the figure 5. The Pacific is the calmest of seas, and the Atlantic Ocean is the most stormy.

The Antarctic Ocean extends from the Antarctic Polar Circle to the South Pole.

It is remarkable that one half of the globe should be entirely covered with water, whilst the other contains less of water than dry land. Moreover, the distribution of land and water, if, in considering the germ of the oceanic basins, we compare the hemispheres separated by the Equator and the northern and southern halves of the globe, is found to be very unequal.

Oceans communicate with continents and islands by coasts, which are said to be scarped when a rocky coast makes a steep and sudden descent to the sea, as in Brittany, Norway, and the west coast of the British Islands. In this kind of coast certain rocky indentations encircle it, sometimes above, sometimes under water, forming a labyrinth of islands, as at the Land's End, Cornwall, where the Scilly Islands form a compact group of from one to two hundred rocky islets, rising out of a deep sea; or in the case of the Channel, on the opposite coast of France, where the coast makes a sudden descent, forming steep cliffs and leaving an open sea. The coast is said to be flat when it consists of soft argillaceous soil descending to the shore with a gentle slope. Of this description of coast there are two, namely, sandy beaches, and hillocks or dunes.

What is the average depth of the sea? It is difficult to give an exact answer to this question, because of the great difficulty met with in taking soundings, caused chiefly by the deviations of submarine currents. No reliable soundings have yet been made in water over five miles in depth.

Laplace found, on astronomical consideration, that the mean depth of the ocean could not be more than ten thousand feet. Alexander von Humboldt adopts the same figures. Dr. Young attributes to the Atlantic a mean depth of a thousand yards, and to the Pacific, four thousand. Mr. Airy, the Astronomer Royal, has laid down a formula, that waves of a given breadth will travel with certain velocities at a given depth, from which it is estimated that the average depth of the North Pacific, between Japan and California, is two thousand one hundred and forty-nine fathoms, or two miles and a half. But these estimates fall far short of the soundings reported by navigators, in which, as we shall see, there are important and only recently discovered elements of error. Du Petit Thouars, during his scientific voyage in the frigate Venus, took some very remarkable soundings in the Southern Pacific Ocean: one, without finding bottom at two thousand four hundred and eleven fathoms; another, in the equinoctial region, indicated bottom at three thousand seven hundred and ninety.

In his last expedition, in search of a north-west passage, Captain Ross found soundings at five thousand fathoms. Lieutenant Walsh, of the American Navy, reports a cast of the deep-sea lead, not far from the American coast, at thirty-four thousand feet without bottom. Lieutenant Berryman reported another unsuccessful attempt to fathom mid ocean with a line thirty-nine thousand feet in length. Captain Denman, of H. M. S. Herald, reported bottom in the South Atlantic at the depth of forty-six thousand feet; and Lieutenant J. P. Parker, of the United States frigate Congress, on attempting soundings near the same region, let go his plummet, after it had run out a line fifty thousand feet long, as if the bottom had not been reached. We have the authority of Lieutenant Maury for saying, however, that "there are no such depths as these." The under-currents of the deep sea have power to take the line out long after the plummet has ceased to sink, and it was before this fact was discovered that these great soundings were reported. It has also been discovered that the line, once dragged down into the depths of the ocean, runs out unceasingly. This difficulty was finally overcome by the ingenuity of Midshipman Brooke. Under the judicious patronage of the Secretary to the United States Navy, Mr. Brooke invented the simple and ingenious apparatus (Fig. 1), by which soundings are now made, in a manner which not only establishes the depth, but brings up specimens of the bottom. The sounding-line in this apparatus is attached to a weighty rod of iron, the lower extremity of which contains a hollow cup for the reception of tallow or some other soft substance. This rod is passed through a hole in a thirty-two pound spherical shot, being supported in its position by slings A, which are hooked on to the line by the swivels a. When the rod strikes the bottom, the tension on the line ceases, the swivels are reversed, the slings B are thrown out of the hooks, the ball falls to the ground, and the rod, released from its weight, is easily drawn up, bringing with it portions of the bottom attached to the greasy substance in the cup. By means of this apparatus, specimens of the bottom have been brought up from the depth of four miles.

Fig. 1. Brooke's Sounding Apparatus.

The greatest depth at which the bottom has been reached with this plummet is in the North Atlantic between the parallels of thirty-five and forty degrees north, and immediately south of the great bank of rocks off Newfoundland. This does not appear to be more than twenty-five thousand feet deep. "The basin of the Atlantic," says Maury, "according to the deep-sea soundings in the accompanying diagram, is a long trough separating the Old World from the New, and extending, probably, from pole to pole. In breadth, it contrasts strongly with the Pacific Ocean. From the top of Chimborazo to the bottom of the Atlantic, at the deepest place yet reached by the plummet in that ocean, the distance in a vertical line is nine miles."

"Could the waters of the Atlantic be drawn off, so as to expose to view this great sea gash which separates continents, and extends from the Arctic to the Antarctic Seas, it would present a scene the most rugged, grand, and imposing; the very ribs of the solid earth with the foundations of the sea would be brought to light, and we should have presented to us in one view, in the empty cradle of the ocean, 'a thousand fearful wrecks,' with the array of 'dead men's skulls, great anchors, heaps of pearls, and inestimable stones,' which, in the poet's eye, lie scattered on the bottom of the sea, making it hideous with the sight of ugly death."

The depth of the Mediterranean is comparatively inconsiderable. Between Gibraltar and Ceuta, Captain Smith estimates the depth at about five thousand seven hundred feet, and from one to three thousand in the narrower parts of the straits. Near Nice, Saussure found bottom at three thousand two hundred and fifty. It is said that the bottom is shallower in the Adriatic, and does not exceed a hundred and forty feet between the coast of Dalmatia and the mouths of the Po.

The Baltic Sea is remarkable for its shallow waters, its maximum rarely exceeding six hundred feet.

It thus appears that the sea has similar inequalities to those observed on land; it has its mountains, valleys, hills, and plains.

The Deep-sea Sounding Apparatus of Lieutenant Brooke has already furnished some very remarkable results. Aided by it, Dr. Maury has constructed his fine orographic map of the basin of the Atlantic, which is probably as exact as the maps which represent Africa or Australia. Dr. Maury has also published many charts, giving the depths of the ocean, the substance of which is given in the accompanying map, which represents the configuration of the Atlantic up to the tenth degree of south latitude, not in figures, as in Dr. Maury's charts, but in tints; diagonal lines from right to left, representing the shores of both hemispheres, indicate a depth of less than a thousand fathoms; from left to right, indicate bottom at one thousand to two thousand; horizontal lines, two to three thousand fathoms; cross lines show an average depth of three to four thousand fathoms; finally, the perpendicular lines indicate a depth of four thousand fathoms and upwards. Solid black indicates continents and islands; waving lines, surrounding both continents at a short distance from the shore, indicate the sands which surround the coast line at a little distance from the shore.

Fig. 2. Chart of the Atlantic Ocean.

The question may be asked, what useful purpose is served by taking soundings at great depths? To this we may quote the answer of Franklin to a question of similar tendency, addressed to aeronauts—"What purpose is served by the birth of a child?" Every fact in physics is interesting in itself; it forms a rallying point, round which, sooner or later, others will meet, in order to establish some useful truth; and the importance of making and recording deep-sea soundings is established by the successful immersion of the transatlantic telegraph.

At the bottom of the Atlantic there exists a remarkable plateau, extending from Cape Race in Newfoundland, to Cape Clear in Ireland, a distance of over two thousand miles, with a breadth of four hundred and seventy miles: its mean depth along the whole route is estimated at two miles to two miles and a half. It is upon this telegraphic plateau, as it has been called, that the attempt was made to lay down the cable in 1858, and it is on it that the enterprise has been so successfully completed, during the year 1866. Tubular annelids, capable of boring into all organic substances, are native to this plateau, and have materially assisted in destroying the electric cable. The surface of the plateau had been previously explored by means of Brooke's apparatus, and the bottom was found to be composed chiefly of microscopic calcareous shells (Foraminifera), and a few siliceous shells (Diatomaceæ). These delicate and fragile shells, which seemed to strew the bottom of the sea, in beds of great thickness, were brought up by the sounding-rod in a state of perfect preservation, which proves that the water is remarkably quiet in these depths,—an inference which is fully borne out by the condition in which the cable of 1858 was found, when picked up in 1866.

Fig. 3. Section of the Atlantic,
showing its depth and the position of
the Atlantic Telegraph.

The first exploration of this plateau was undertaken by the American brig Dolphin, which took a hundred soundings one hundred miles from the coast of Scotland, afterwards taking the direction of the Azores, to the north of which bottom was found, consisting of chalk and yellow sand, at nine thousand six hundred feet. To the south of Newfoundland, the depth was found to be sixteen thousand five hundred feet. In 1856, Lieutenant Berryman, of the American steamer Arctic, completed a line of soundings from St. John, Newfoundland, to Valentia, off the Irish coast, and in 1857, Lieutenant Dayman, of the English steamship Cyclops, repeated the same operation: this last line of soundings, the result of which is represented in the accompanying section, differed slightly from that followed by Lieutenant Berryman.

In the Gulf of Mexico, the depth does not seem to exceed seven thousand feet; the Baltic does not in any place exceed eleven hundred. The depth of the Mediterranean is, as we have said, very variable. At Nice, according to Horace de Saussure, the average depth is three thousand three hundred feet. Between the Dalmatian coast and the mouth of the Po, bottom is found at a hundred and forty feet. Captain Smith found soundings at from one thousand to nine thousand feet in the Straits of Gibraltar, and at ten thousand feet between Gibraltar and Ceuta, where the breadth exceeds sixteen miles. Between Rhodes and Alexandria, the greatest depth is ten thousand feet. Between Alexandria and Candia it is ten thousand three hundred. A hundred and twenty miles east of Malta it is fifteen thousand. The peculiar form of the Mediterranean has led to its being compared to a vast inverted tunnel.

The Arctic Ocean has, probably, no great depth. Hence salt water, following the general law of contracting as it is cooled until it freezes, no ice can be formed on its surface till the temperature has fallen through its entire depth nearly to freezing point, when the entire mass is consolidated into pack-ice. According to Baron Wrangel, the bottom of the glacial sea, on the north coast of Siberia, forms a gentle slope, and, at the distance of two hundred miles from the shore, it is still only from ninety to a hundred feet. Nevertheless, in Baffin's Bay, Dr. Kane made soundings at eleven thousand six hundred feet.

The inequalities of the basin of the Pacific Ocean are, comparatively, unknown to us. The greatest depth observed by Lieutenant Brooke in the great ocean is two thousand seven hundred fathoms, which he found in fifty-nine degrees north latitude and one hundred and sixty-six degrees east longitude. Applying the theory of waves to the billows propelled from the coast of Japan to California, during the earthquake of the 23rd of December, 1854, Professor Bache calculated that the mean depth of this part of the Pacific is fourteen thousand four hundred feet. In the Pacific Ocean, latitude sixty degrees south and one hundred and sixty degrees east longitude, he found soundings at fourteen thousand six hundred feet—about two miles and a half. Another cast of the lead in the Indian Ocean was made in seven thousand and forty fathoms, but without bringing up any soil from the bottom. Among the fragments brought up from the bottom of the Coral Sea, a remarkable absence of calcareous shells was noted, whilst the siliceous fragments of sponges were found in great quantities. Other soundings made in the Pacific, at a depth of four or five miles, were examined by Ehrenberg, who found a hundred and thirty-five different forms of infusoria represented, and among them twenty-two species new to him. Generally speaking, the composition of the infusoria of the Atlantic are calcareous; those of the Pacific, siliceous. These animalcules draw from the sea the mineral matter with which it is charged—that is, the lime or silica which form their shell. These shells accumulate after the death of the animal, and form the bottom of the ocean. The animals construct their habitations near the surface; when they die, they fall into the depths of the ocean, where they accumulate in myriads, forming mountains and plains in mid ocean. In this manner, we may remark, en passant, many of the existing continents had their birth in geological times. The horizontal beds of marine deposits, which are called sedimentary rocks, and especially the cretaceous rocks and calcareous beds of the Jurassic and Tertiary periods, all result from such remains.[1]

The sea level is, in general, the same everywhere. It represents the spherical form of our planet, and is the basis for calculating all terrestrial heights; but many gulfs and inland seas open on the east are supposed to be exceptions to this rule: the accumulation of waters, pressed into these receptacles by the general movement of the sea from east to west, it is alleged, may pile up the waters, in some cases, to a greater height than the general level.

It had long been admitted, on the faith of inexact observation, that the level of the Red Sea was higher than that of the Mediterranean. It has also been said that the level of the Pacific Ocean at Panama is higher by about forty inches than the mean level of the Atlantic at Chagres, and that, at the moment of high water, this difference is increased to about thirteen feet, while at low it is over six feet in the opposite direction. This has been proved, so far as the evidence goes, to be error in what concerns the difference in level of the Red Sea and Mediterranean; and the opening of the Suez Canal, which is near at hand, will probably furnish still more convincing proofs. Recent soundings show that the mean level of the Pacific and Atlantic Oceans are identical.

It has been calculated that all the waters of the several seas gathered together would form a sphere of fifty or sixty leagues in diameter, and, supposing the surface of the globe perfectly level, that these waters would submerge it to the depth of more than six hundred feet. Again, admitting the mean depth of the sea to be thirteen thousand feet, its estimated contents ought to be nearly two thousand two hundred and fifty millions of cubic miles of water; and, if the sea could be imagined to be dried up, all the sewers of the earth would require to pour their waters into it for forty thousand years, in order to fill the vast basins anew.

If we could imagine the entire globe to be divided into one thousand seven hundred and eighty-six parts by weight, we should find approximately, according to Sir John Herschel, that the total weight of the oceanic waters is equivalent to one of these parts.

The specific weight of sea water is a little above that of fresh water, the proportion being as a thousand to a thousand and twenty-seven. The Dead Sea, which receives no fresh water into its bosom to maintain itself at the same level as other seas, acquires a higher degree of saltness, and is equal to a thousand and twenty-eight. The specific gravity of sea water is about the same as the milk of a healthy woman.

The colour of the sea is continually varying, and is chiefly caused by filtration of the solar rays. According to the testimony of the majority of observers, the ocean, seen by reflection, presents a fine azure blue or ultramarine (cæruleum mare). When the air is pure and the surface calm this tint softens insensibly, until it is lost and blended with the blue of the heavens. Near the shore it becomes more of a green or glaucus, and more or less brilliant, according to circumstances. There are some days when the ocean assumes a livid aspect, and others when it becomes a very pure green; at other times, the green is sombre and sad. When the sea is agitated, the green takes a brownish hue. At sunset, the surface of the sea is illumined with tints of every hue of purple and emerald. Placed in a vase, sea water appears perfectly transparent and colourless. According to Scoresby, the Polar seas are of brilliant ultramarine blue. Castaz says of the Mediterranean, that it is celestial blue, and Tuckey describes the equinoctial Atlantic as being of a vivid blue.

Many local causes influence the colours of marine waters, and give them certain decided and constant shades. A bottom of white sand will communicate a greyish or apple-green colour to the water, if not very deep; when the sand is yellow, the green appears more sombre; the presence of rocks is often announced by the deep colour which the sea takes in their vicinity. In the Bay of Loango the waters appear of a deep red, because the bottom is there naturally red. It appears white in the Gulf of Guinea, yellow on the coast of Japan, green to the west of the Canaries, and black round the Maldive group of islands. The Mediterranean, towards the Archipelago, sometimes becomes more or less red. The White and Black Seas appear to be named after the ice of the one and the tempests to which the other is subject.

At other times, coloured animalcules give to the water a particular tint. The Red Sea owes its colour to a delicate microscopic algæ (Trychodesmium erythræum), which was subjected to the microscope by Ehrenberg; but other causes of colouration are suggested. Some microscopists maintain that it is imparted by the shells and other remains of infusoria; others ascribe the colour to the evaporation which goes on unceasingly in that riverless district, producing salt rocks on a great scale all round its shores. In the same manner sea water, concentrated by the action of the solar rays in the salt marshes of the south of France, when they arrive at a certain stage of concentration take a fine red colour, which is due to the presence of some red-shelled animalcules which only appear in sea water of this strength. The saline lakes on the Great Thibetian water sheds are due to this cause. Strangely enough, these minute creatures die when the waters attain greater density by further concentration, and also if it becomes weaker from the effects of rain.

Navigators often traverse long patches of green, red, white, or yellow coloured water, all of which are due to the presence of microscopic crustaceans, medusæ, zoophytes, and marine plants; the Vermilion Sea on the Californian coast is entirely due to the latter cause.

The phenomenon known as Phosphorescence of the Sea is due to analogous causes. This wonderful sight is observable in all seas, but is most frequent in the Indian Ocean, the Arabian Gulf, and other tropical seas. In the Indian Ocean, Captain Kingman, of the American ship Shooting Star, traversed a zone twenty-three miles in length so filled with phosphorescent animalcules that at seven hours forty-five minutes the water was rapidly assuming a white, milky appearance, and during the night it presented the appearance of a vast field of snow. "There was scarcely a cloud in the heavens," he continues, "yet the sky, for about ten degrees above the horizon, appeared as black as if a storm were raging; stars of the first magnitude shone with a feeble light, and the 'Milky Way' of the heavens was almost entirely eclipsed by that through which we were sailing." The animals which produced this appearance were about six inches long, and formed of a gelatinous and translucent matter. At times, the sea was one blaze of light, produced by countless millions of minute globular creatures, called Noctilucæ. The motion of a vessel or the plash of an oar will often excite their lucidity, and sometimes, after the ebb of tide, the rocks and seaweed of the coast are glowing with them. Various other tribes of animals there are which contribute to this luminous appearance of the sea. M. Peron thus describes the effect produced by Pyrosoma Atlanticum, on his voyage to the Isle of France: "The wind was blowing with great violence, the night was dark, and the vessel was making rapid way, when what appeared to be a vast sheet of phosphorus presented itself floating on the waves, and occupying a great space ahead of the ship. The vessel having passed through this fiery mass, it was discovered that the light was occasioned by animalcules swimming about in the sea at various depths round the ship. Those which were deepest in the water looked like red-hot balls, while those on the surface resembled cylinders of red-hot iron. Some of the latter were caught: they were found to vary in size from three to seven inches. All the exterior of the creatures bristled with long thick tubercles, shining like so many diamonds, and these seemed to be the principal seat of their luminosity. Inside also there appeared to be a multitude of oblong narrow glands, exhibiting a high degree of phosphoric power. The colour of these animals when in repose is an opal yellow, mixed with green; but, on the slightest movement, the animal exhibits a spontaneous contractile power, and assumes a luminous brilliancy, passing through various shades of deep red, orange, green, and azure blue."

The phosphorescence of the sea is a spectacle at once imposing and magnificent. The ship, in plunging through the waves, seems to advance through a sea of red and blue flame, which is thrown off by the keel like so much lightning. Myriads of creatures float and play on the surface of the waves, dividing, multiplying, and reuniting, so as to form one vast field of fire. In stormy weather the luminous waves roll and break in a silvery foam. Glittering bodies, which might be taken for fire-fishes, seem to pursue and catch each other—lose their hold, and dart after each other anew. From time immemorial, the phosphorescence of the sea has been observed by navigators. The luminous appearance presents itself on the crest of the waves, which in falling scatters it in all directions. It attaches itself to the rudder and dashes against the bows of the vessel. It plays round the reefs and rocks against which the waves beat, and on silent nights, in the tropics, its effects are truly magical. This phosphorescence is due chiefly to the presence of a multitude of mollusks and zoophytes which seem to shine by their own light; they emit a fluid so susceptible of expansion, that in the zigzag movement pursued they leave a luminous train upon the water, which spreads with immense rapidity. One of the most remarkable of these minute mollusks is a species of Pyrosoma, a sort of mucous sac of an inch long, which, thrown upon the deck of a ship, emits a light like a rod of iron heated to a white heat. Sir John Herschel noted on the surface of calm water a very curious form of this phosphorescence; it was a polygon of rectilinear shape, covering many square feet of surface, and it illuminated the whole region for some moments with a vivid light, which traversed it with great rapidity.

The phosphorescence of the sea may also result from another cause. When animal matter is decomposed, it becomes phosphorescent. The bodies of certain fishes, when they become a prey to putrefaction, emit an intense light. MM. Becquerel and Breschet have noted fine phosphorescent effects from this cause in the waters of the Brenta at Venice. Animal matter in a state of decomposition, proceeding from dead fish which floats on the surface of ponds, is capable of producing large patches of oleaginous matter, which, piled upon the water, communicates to a considerable extent the phosphorescent aspect.

Whatever may be the case elsewhere, there are local causes which affect the colour of the waters in certain rivers, and even originate their names. The Guaïnia, which with the Casiquaire forms the Rio Negro, is of a deep brown, which scarcely interferes with the limpidity of its waters. The waters of the Orinoco and the Casiquaire have also a brownish colour. The Ganges is of a muddy brown, while the Djumna, which it receives, is green or blue. The whitish colour belongs to the Rio Bianco, or White River, and to many other rivers. The Ohio in America, the Torgedale, the Goetha, the Traun at Ischl, and most of the Norwegian rivers, are of a delicate limpid green. The Yellow River and the Blue River in China are distinguished by the characteristic tint of their waters. The Arkansas, the Red River, and the Lobregat in Catalonia, are remarkable for their red colour, which, like the Dart and other English rivers, they owe to the earth over which they flow, or which their waters hold in suspension.

The water of the sea is essentially salt, of a peculiar flavour, slightly acrid and bitter, and a little nauseous. It has an odour perfectly sui generis, and is slightly viscous. In short, it includes a great number of mineral salts and some other compounds, which give it a very disagreeable taste, and render it unfit for domestic use. It contains nearly all the soluble substances which exist on the globe, but principally chloride of sodium, or marine salt, and sulphate of magnesia, of potassium, and of lime.

Pure water is produced by a combination of one volume of oxygen and of two volumes of hydrogen, or in weight, 100 oxygen and 12·50 hydrogen. Sea water is composed of the same; but we find there, besides, other elements, the presence of which chemistry reveals to us. In 1000 grains of sea water the following ingredients are found:—

consisting of sulphuretted hydrogen, hydrochlorate of ammonia, iodine iron, copper, and even silver in various quantities and proportions, according to the locality of the specimen. In examining the plates of copper taken from the bottom of a ship at Valparaiso, which had been long at sea, distinct traces of silver were found deposited by the sea. Finally, we find dissolved in the ocean a peculiar mucus, which seems of a mixed animal and vegetable nature, and is evidently organic matter proceeding from the successive decomposition of the innumerable generations of animals which have disappeared since the beginning of the world. This matter has been described by the Count Marsigli, who designates it sometimes under the name of glu, and sometimes as an unctuosity. It is the "ooze" of marine surveyors, and consists chiefly of carbonate of lime, ninety per cent. of which is formed of minute animal organisms. Its mealy adhesiveness results from the pressure of the superimposed water. The numerous salts which exist in the sea can neither be deposited in its bed, nor exhaled with the vapour, to be again poured upon the soil in showers of rain. Particular agents retain these salts in solution, transform them, and prevent their accumulation. Hence sea water always maintains a certain degree of saltness and bitterness, and the ocean continues to present the chemical characters which it has exhibited in all times, varying only in certain localities where more or less fresh water is poured into the sea basin from rivers: thus the saltness of the Mediterranean is greater than that of the ocean, probably because it loses more water by evaporation than it receives from its fresh-water affluents. For the opposite reason, the Black and the Caspian Seas are less charged with these salts. The Dead Sea is so strongly impregnated with salt that the body of a man floats on its surface without sinking, like a piece of cork upon fresh water. The supposed cause is excessive evaporation and the absence of rivers of any importance.

The saltness of the sea seems to be generally less towards the poles than the equator; but there are exceptions to this law. In the Irish Channel, near the Cumberland coast, the water contains salt equal to the fortieth of its weight; on the coast of France, it is equal to one thirty-second; in the Baltic, it is equal to a thirtieth; at Teneriffe, a twenty-eighth; and off the coast of Spain, to a sixteenth. Again, in many places the sea is less salt at the surface than at the bottom. In the Straits of the Dardanelles, at Constantinople, the proportion is as seventy-two to sixty-two. In the Mediterranean, it is as thirty-two to twenty-nine. It is also stated that as the salt increases at a certain depth, the water becomes less bitter. At the mouth of the great rivers it is scarcely necessary to add that the water is always less saline than on shores which receive no supplies of fresh water; the same remark applies to sea water in the vicinity of polar ice, the melting of which is productive of much fresh water. A recent analysis of the water of the Dead Sea by M. Roux gives about two pounds of salt to one gallon of water. No mineral water, if we except that of the Salt Lake of Utah, is so largely impregnated with saline substances; the quantity of bromide of magnesia is 0·35 grammes to the litre. The water of the Dead Sea is, according to these proportions, the richest natural depository of bromide, which it might be made to furnish abundantly. The waters of the great Lake of Utah and Lake Ourmiah in Persia are both highly saline. In Lake Ourmiah, as in the Dead Sea, the proportion of salt is six times greater than in the ocean. Many of our fresh-water lakes were probably salt originally, but have by degrees lost their saline properties by the mingling of their waters with those of the rivers which traverse or flow into them. Among the lakes which appear to have been divested of their saline properties may be mentioned the great lakes of Canada and the Sea of Baikal, in all of which seals and other marine animals are still found, which have become acclimatized as the water gradually became fresh.

The saltness of sea water increases its density, and at the same time its buoyancy, thus adapting it for bearing ships and other burdens on its bosom; moreover, to abbreviate slightly Dr. Maury's remark, "the brine of the ocean is the ley of the earth." From it the sea derives dynamical power, and its currents their main strength. It is the salt of the sea that imparts to its waters those curious anomalies in the laws of freezing and of thermal dilatation, that assist the rays of heat to penetrate its bosom; the salts of the sea invest it with adaptations which fresh water could not possess. In the latter case, the maximum density would be thirty-nine degrees two seconds F. instead of twenty-seven degrees two seconds F., when the dynamical force of the sea would be insufficient to put the Gulf Stream in motion. Nor could it regulate those climates we call marine.

We have said that sea water contains nearly all the soluble substances which exist in the globe. Nevertheless its exhalation is comparatively pure. "The water which evaporates from the sea," says Youman, in his "Chemistry," "is nearly pure, containing but very minute traces of salts. Falling as rain upon the land, it washes the soil, percolates through the rocky layers, and becomes charged with saline substances, which are borne seaward by the returning currents. The ocean, therefore, is the great depository of all substances that water can dissolve and carry down from the surface of the continents; and, as there is no channel for their escape, they would constantly accumulate, were it not for the creatures which inhabit the seas, and utilize the material thus brought within their reach." These substances are chloride of sodium or marine salt, sulphates of magnesia, potassa, lime, and other substances which the water of various seas is found to contain.

In the year 1847, I made an analysis of water taken a few leagues from the coast at Havre, which gave the following result, from one litre (1 pint·760773):—[2]

The water of the Mediterranean contains more salts than that of the ocean.

The following are, according to M. Usiglio, who was one of a commission sent to examine the different kinds of salt water in the south of France, the component parts of one hundred gallons of Mediterranean water:—

We conclude, from the quantity of sea salt contained in the water of the ocean, that, if it were spread over the surface of the globe, it would form a layer of more than thirty feet in height.

The salt contained in sea water gives it a greater density than fresh water; its average specific weight is 1.027. The density of the water of the Mediterranean is, according to M. Usiglio, 1.025 when at the temperature of seventy degrees. But the saltness of the sea varies very much under the influence of a great many local circumstances, among which we must count principally currents, winds favourable to evaporation, rivers coming from the continents, &c.

It has been remarked that the sea is less salt towards the poles than at the equator; that the saltness increases, in general, with the distance from land, and the depth of the water; that the interior seas, such as the Baltic, the Black Sea, the White Sea, the Sea of Marmora, and the Yellow Sea, are less salt than the ocean. The Mediterranean is an exception to this last rule; it is, as we have seen, salter than the ocean. This difference is explained by the fact that the quantity of fresh water brought into it by rivers is less than that lost by evaporation. The Mediterranean must therefore grow salter with time, unless its water is discharged into the ocean by a counter current, which would run under the current coming from the Atlantic by the Straits of Gibraltar.

The Black Sea, on the contrary, the water of which has a density of only 1.013, receives from rivers more fresh water than it loses by evaporation. The saltness of this interior sea is only half as intense as that of the ocean.

The Sea of Azov and the Caspian Sea are still less salt than the Black Sea.

The following table shows the relative composition of the water in these three interior seas:—

In lakes without any outlet, as the Dead Sea and the Lake of Ural, the degree of saltness is considerably augmented. Numerous experiments have proved that the water of the Dead Sea is six times salter than that of the ocean. MM. Boutron and O'Henry analysed, in April, 1850, after the rainy season, some water of the Dead Sea, taken at about two leagues from the mouth of the Jordan; its density was then 1·10.

The saltness of sea water makes it more fitted to float ships, because its density is increased by the salts which are dissolved in it. Besides this, these salts contribute to prevent the water becoming contaminated with decomposed organic matter.

By the table representing the composition of the water of the ocean and of that of the Mediterranean, we see that salts of lime and potassium, as well as iodine and silica, are only found in infinitely small quantities. Nevertheless, the lime and silica contained in the sea water are of very great importance; for these quantities, which appear to us so small in the table of a chemical analysis, become enormous in the entire extent of the ocean. The marine plants take in the lime, the silica, the potassa, and the iodides which are dissolved in the sea water; these mineral substances enter into their textures. It is from the carbonate of lime and silica that the marine animals form their solid covering, their shell or carapace. The infusoria make use of the lime, silica, and potassa for the same purpose. It is by the life and habits of the polypi that we explain those Coral Islands found in the sea, the existence of which has been a subject of much astonishment, and ought, therefore, to find a place in this chapter.

The Pacific and Indian Oceans are studded with islands in a state of formation, which owe their origin to the polypi and corallines. These zoophytes extract from the sea water the lime and silicium which are found there in the state of soluble salts. In order to grow and develop, they must be continually under water. They are constantly producing calcareous deposits; these deposits rise rapidly, and at last reach the surface of the water. Then the seaweed and rubbish of all kinds that the sea carries along with it, arrested by these emerged masses, cover them with a layer of fertile soil; which is soon covered with vegetation, as the birds and the waves bring seeds thither.

The Coral Islands of the Pacific, which are described in another chapter, are formed in this manner.

Besides the substances named, sea water also contains, in infinitesimally small quantities, metals, such as iron, copper, lead and silver. The old copper collecting round the keels of ships sometimes so much silver that it has been thought worth extracting! A curious calculation has been attempted, based on the age of ships and the distance they have gone during all their voyages, to show that the sea contains in solution two million tons of silver.[3]

The question has often been asked, whence comes the salt and other substances held in solution in sea water? If our readers will turn back to the first few pages of "The World before the Deluge," they will better understand the very simple geological explanation that we are going to give of the origin of different substances dissolved in sea water.

In the first stage of our planet, before the watery vapours contained in the primitive atmosphere were condensed, and before they had begun to fall on the earth in the form of boiling rain, the shell of the earth contained an infinite variety of heterogeneous mineral substances, some soluble in water, others not. When rain fell on the burning surface for the first time, the waters became charged with all the soluble substances, which were reunited and afterwards deposited, accumulating in the large depressions of the soil. The seas of the primitive globe were thus formed of rain water, holding in solution all that the earth had given up, collected in large basins. Chloride of sodium, sulphates of soda, magnesia, potassium, lime, and silica, in the form of soluble silicate; in a word, every soluble matter that the primitive globe contained formed part of the mineral contingent of this water. If we reflect that through all time up to the present day none of the general laws of nature have changed—if we consider that the soluble substances contained in the water of the primitive seas have remained there, and that the fresh water of the rivers constantly replaces the water which disappears by evaporation—we have the true explanation of the saltness of sea water. "It is a very simple theory, it is true," adds M. Figuier, "but one that we have found nowhere, and the responsibility of which we therefore claim. The chloride of sodium is by no means the only substance dissolved in sea water. It contains, besides, many other mineral substances: in short, every soluble salt on the face of the globe, and, along with them, portions of different metals in infinitely small quantities."

The mean temperature of the surface of the sea is nearly the same as the atmosphere, so long as no currents of heat or cold interpose their perturbing influence. In the neighbourhood of the Tropics, it appears that the surface of the water is slightly warmer than the ambient air, but experiments on the temperature of the sea from the surface to the bottom reveal, according to our author,[4] "some evidence which establishes a curious law. In very deep water a perfectly uniform temperature of four degrees below zero prevails, which corresponds, as physics have established, to the maximum density of water. Under the Equator this temperature exists at the depth of seven thousand feet. In the Polar regions, where water is colder at the surface, this temperature is maintained at four thousand six hundred feet. The isothermal lines of four degrees form a line of demarcation between the Zones, where the surface of the sea is colder, and those where it is warmer than the bed of four degrees below zero." This is more clearly shown in Fig. 4, which represents a section of the ocean, the curved line which touches two points at the surface indicating the depths where the temperature is constantly fixed at four degrees.

Dr. Maury's account of this phenomenon is asserted with less confidence. The existence of an isothermal floor of the ocean, as he calls it, was first suggested by the observations of Kotzebue, Admiral Beechey, and Sir James C. Ross. "Its temperature, according to Kotzebue, is thirty-six degrees Fahr., or four degrees Cent.; the depth of this bed, of invariable and uniform temperature, is twelve hundred fathoms at the Equator; thence it gradually rises to the parallel of about fifty-six degrees north and south, when it crops out, and there the temperature of the sea from top to bottom is conjectured to be permanent at thirty-six degrees. The place of this outcrop, no doubt, shifts with the seasons, vibrating north and south, after the manner of the Calm belts. Proceeding onwards to the Frigid zones, this aqueous stratum of an unchanging temperature dips again, and continues to incline till it reaches the Poles, at the depth of seven hundred and fifty fathoms; so that on the equatorial side of the outcrop the water above the isothermal floor is the warmer, but in Polar seas the supernatant water is the colder."

Fig. 4. Thermal Lines of equal Temperature.

In the saline properties of sea water Maury discovers one of the principal forces from which currents in the ocean proceed. "The brine of the ocean is the ley of the earth," he says; "from it the sea derives dynamical powers, and its currents their main strength. Hence, to understand the dynamics of the ocean, it is necessary to study the effects of their saltness upon the equilibrium of the waves. Why is the sea made salt? It is the salts of the sea that impart to its waters those curious anomalies in the laws of freezing and of thermal dilatation. It is the salts of the sea that assist the rays of heat to penetrate its bosom." The circulation of the ocean is indispensable to the distribution of temperature—to the maintenance of the meteorological and climatic conditions which rule the development of life; and this circulation could not exist—at least, the character of its waters would be completely changed—if they were fresh in place of salt. "Let us imagine," says M. Julien, "that the sea, now entirely composed of fresh water, of one uniform temperature from the Pole to the Equator, and from the surface to its greatest depths; the solar heat would penetrate the liquid beds nearest to the Equator; it would dilate them, so as to raise them above their primitive level; by the single effect of gravitation, they would glide on the surface towards the polar zones. The absence of all solar radiation would tend, on the contrary, to cool and contract them without this tendency. An exchange would be established from the extremities towards the centre; in other words, a counter current of cold and heavy water, calculated to replace the losses occasioned by the action of solar radiation, would descend from the Poles, but quite maintaining itself beneath the light and warm current from the Equator."

In a like system of general circulation, the physical properties of pure water, which attains its maximum of density seven degrees two seconds F. below zero, would produce the most singular consequences. As its temperature rose above that point, the water would become lighter, having, consequently, a tendency to ascend towards the upper beds. After this, the equatorial current, meeting in its progress towards the Poles the cold water, would itself be cooled down; and when its temperature had reached four degrees below zero, being now heavier than the polar current, would change places with it, descending until it reached water equally dense, while the polar current would ascend. Hence would arise a sort of confusion of currents which would give to a fresh-water ocean the strangest results, disarranging every instant the regular circulation of its waters. It could not be so, however, in an ocean of salt water, which attains its maximum specific gravity at four degrees eight seconds F. below zero. By evaporation at the surface it is concentrated and precipitated, and thus rendered denser than that immediately below the surface. It consequently sinks, while the lower beds come up to replace, in order to modify it, and in turn to be precipitated in the same manner. "In this manner we find established a continually ascending and descending movement, which carries down into the depths of ocean the water warmed at the surface by the solar rays of the Torrid zone. This double vertical current facilitates and prepares the grand horizontal current which puts these submarine reservoirs of heat in communication with the lower beds of the glacial sea. In the Arctic basin the clouds, the melted snow, and the great rivers, which have their mouths on the north of both continents, produce considerable quantities of fresh water, which, mixing with the waves of the Polar Sea, form a bed of mean density light enough to maintain itself and flow off towards the Atlantic Ocean. These surface movements determine in the lower regions certain contrary movements, whence originate the powerful counter currents which ascend the Straits from Baffin's Bay and reappear in the mysterious 'Polynia' of Kane, diffusing there its treasure of heat brought from intertropical seas." Dr. Kane, in his interesting Narrative, reports an open sea north of the parallel of eighty-two degrees, which he and his party crossed a barrier of ice eighty miles broad to reach, and before he reached it the thermometer marked sixty degrees. Beyond this ice-bound region he found himself on the shores of an iceless sea, extending in an unbroken sheet of water as far as the eye could reach towards the Pole. Its waves were dashing on the beach with the swell of a great ocean; the tides ebbed and flowed. Now the question arises, Where did those tides have their origin? The tidal wave of the Atlantic could not have passed under the icy barrier which De Haven found so firm; therefore they must have been cradled in the cold sea round the Pole; in which case it follows that most, if not all, the unexplored regions about the Pole must be covered with deep water, the only source of strong and regular tides. Seals were sporting and waterfowl feeding in this open sea, as Dr. Kane tells us, and the temperature of the water which rolled in and dashed at his feet with measured beat was thirty-six degrees, while the bottom of the icy barrier of eighty miles was probably hundreds of feet below the surface level.

"The existence of these tides," says Maury, "with the immense flow and drift which annually take place from the Polar Seas and the Atlantic, suggests many conjectures as to the condition of these unexplored regions. Whalemen have always been puzzled as to the breeding place of the great whale. It is a cold-water animal, and, following up the train of thought, the question arises, Is not the nursery for the great whale in this Polar Sea, which is so set about and hemmed in by a hedge of ice, that man may not trespass there?"

One or two points worthy of notice may be recorded here. Shallow water, and water near the coast, or covering raised sand-banks, is colder than water in the open sea. Alexander von Humboldt explains this phenomenon by supposing that deep waters of higher temperature reascend from the lowest depths and mingle with the upper beds. Fogs are frequently formed over sand-banks, because the cold water which covers them produces a local precipitation of atmospheric vapour. The contour of these fogs are perfectly defined when seen from a distance: they reproduce the form and accidents due to the submarine soil. Moreover, we often see clouds arrested over these points, which look from afar like the peaks of mountains.

CHAPTER II.

CURRENTS OF THE OCEAN.

" * * * * seas that sweep

The three-decker's oaken mast." Tennyson.

The ocean is a scene of unceasing agitation; "its vast surface rises and falls," to use the image suggested by Schleiden, "as if it were gifted with a gentle power of respiration; its movements, gentle or powerful, slow or rapid, are all determined by differences of temperature."

Heat increases its volume and changes the specific gravity of the water, which is dilated or condensed in proportion to the change of temperature. In proportion as it cools, water increases in density, and descends into the depths until it reaches a constant temperature of four degrees twenty-five minutes Cent. below zero, which it preserves in all latitudes at the depth of a thousand yards, according to M. D'Urville.

If the water continues to cool, and reaches zero, it becomes lighter than it was at four degrees twenty-five minutes Cent., and ascends in a state of congelation—a process which, by an admirable provision of nature, can only take place at the surface. So long as the temperature is above four degrees twenty-five minutes, water is light, and ascends to the surface, while colder water sinks to the bottom. Below four degrees twenty-five minutes the process is reversed; the first phenomenon is always in force under the Equator, the second near the Poles. The evaporation, which is in continual operation in warm seas, forming vast rain-clouds at the expense of the sea, is compensated by unceasing currents of colder water flowing from the Poles. This evaporation has a direct influence, moreover, on the density of sea water, and is pointed out by Dr. Maury as a remarkable instance of the compensations by which the oceanic waters are governed: "According to Rodgers' observations," he says, "the average specific gravity of sea water on the parallels of thirty-four degrees north and south, at a mean temperature of sixty-four degrees, is just what it ought to be, according to saline and thermal laws; but its specific gravity, when taken from the Equator at a mean temperature of eighty-one degrees, is much greater than, according to the same laws, it ought to be—the observed difference being ·0015, whereas it ought to be ·0025. Let us inquire," he adds, "what makes the equatorial waters so much heavier than they ought to be.

"The anomaly occurs in the trade-wind region, and is best developed between the parallel of forty degrees in the North Atlantic and the Equator, where the water grows warmer, but not proportionally lighter. The water sucked up by the trade-winds is fresh water, and the salt it contained, being left behind, is just sufficient to counteract by its weight the effect of thermal dilatation upon the specific gravity of water between the parallels of thirty-four degrees north and south. The thirsting of the trade-winds for vapour is so balanced as to produce perfect compensation, and a more beautiful instance than we have here stumbled upon is not, it appears to me, to be found in the mechanism of the universe."

The oceanic currents are due to a great number of causes: the duration and force of the winds, for instance; the rise and fall of tides all over the globe; the variations in the density of the waters, according to its temperature, and the evaporating powers of the atmosphere; the depth and degree of saltness to which we have already alluded; finally, to the variations of barometric pressure.

The currents which furrow the ocean present a striking contrast with the immobility of the neighbouring waters; they form rivers of a determinate breadth, whose banks are formed by the water in repose, and whose course is often made quite perceptible by the vrachs and other aquatic plants which follow in their train.

In order to comprehend the origin of these pelagic rivers, it is necessary to consider the laws which govern the atmospheric currents, in particular the trade-winds. "Hence," says Maury, "in studying the system of oceanic circulation, we set out with the very simple assumption, that from whatever part of the ocean a current is found to run, to that same part a current of equal volume is bound to return; for on this principle is based the whole system of currents and counter currents." The differences of temperature between equinoctial and polar countries generate two opposing currents, the upper one proceeding from the Equator to the Poles, the lower one directed from the Poles towards the Equator. On reaching the Equator, the cold current of air from the Poles is warmed and rarefied, and ascends to the upper beds of the atmosphere, whence it is again led to its point of departure; there it is again cooled, and returns with the lower current towards the tropical regions. But the rotatory movement of the earth modifies the direction of these atmospheric currents. The movement by which it is carried from west to east being almost nothing at the Poles, but inconceivably rapid under the Equator, it follows that the cold air, in proportion as it advances towards the Tropics, ought to incline a little towards the west. This is just what takes place with these counter currents. The north-east trade-winds, which prevail in the northern hemisphere, move in a sort of spiral curve, turning to the west as they rush from the Poles to the Equator, and in the opposite direction as they move from the Equator towards the Poles; the immediate cause of this motion being the rotation of the earth on its axis. "The earth," says Dr. Maury, "moves from west to east. Now, if we imagine a particle of atmosphere at the North Pole, where it is at rest, to be put in motion in a straight line towards the Equator, we can easily see how this particle of air, coming from the very axis of diurnal rotation, where it did not partake of the diurnal motion, would, in consequence of its own vis inertiæ, find as it travelled south that the earth was slipping from under it, as it were, and it would appear to be coming from the north-east and going towards the south-west; in other words, it would be a north-east wind."

In the same manner, the upper currents of air, which proceed towards the Poles with equatorial rapidity, ought to outstrip the atmospheric beds, which are gifted with much smaller rapidity of motion towards the Poles, and turn them towards the east in consequence. These are the south-west and north-west counter trade-winds, which, passing above the north and south-east trades, often sweep the surface of the sea in the latitudes of the Temperate zone. The two trades are separated by a belt more or less broad, where the friction experienced at the surface of the sea neutralizes their impulse towards the west; in general, the current of air there is an ascending current. This belt, which does not exactly correspond with the Equator, is called the Zone of Calms, where atmospheric tempests frequently occur, and the winds make the entire tour of the compass, which has acquired for them the name of tornadoes.

The trade-winds, whose movement towards the west is retarded by the friction which the waves of the ocean oppose to them, communicate to these waves, by a sort of reaction, a tendency towards the west, or, to speak more exactly, towards the south-west in the northern hemisphere, and towards the north-west in the opposite hemisphere. The currents on the surface of the water which result from this reaction, reunite under the Equator, and form the grand equinoctial current which impels the waters of the east towards the west. This movement is stronger at the edges than in the middle of the current, because the force which produces it acts there with more energy: it results from this, that the currents bifurcate more readily when any obstacle presents itself to its movement. In the Atlantic Ocean, bifurcation takes place a little to the south of the Equator; the southern branch descends along the coast of Brazil, and probably returns by reascending along the west coast of Africa. The northern branch follows the coast of Brazil and Guiana, enters the Sea of the Antilles, and directs its course, reinforced by the current which reaches it from the north-east, into the Bay of Honduras, traverses the Yucatan Channel, and enters the Gulf of Mexico, whence it debouches by the Florida Channel, under the name of the Gulf Stream. Of this oceanic marvel Dr. Maury observes that "there is a river in the bosom of the ocean; in the several droughts it never fails, and in the mightiest floods it never overflows; its banks and its bottom are of cold water, while its current is of warm; it takes its rise in the Gulf of Mexico, and empties itself into the Arctic Seas. This mighty river is the Gulf Stream. In no other part of the world is there such a majestic flow of water; its current is more rapid than the Amazon, more impetuous than the Mississippi, and its volume is more than a thousand times greater. Its waters, as far as the Carolina coast, are of indigo blue; they are so distinctly indicated that their line of junction can be marked by the eye." Such is Dr. Maury's description of this powerful current of warm water, which traverses the Atlantic Ocean, and influences in no slight manner the climate of Northern Europe, and especially our own shores.

The Gulf Stream thus described by the American savant issues from the Florida Channel, with a breadth of thirty-four miles, and a depth of two thousand two hundred feet, moving at the rate of four and a half miles per hour. The temperature of the water in the vicinity is about thirty degrees Cent. From the American coast the current takes a north-east direction towards Spitzbergen, its velocity and volume diminishing as it expands in breadth. Towards the forty-third degree of latitude it forms two branches, one of which strikes the coast of Ireland and of Norway, whither it frequently transports seeds of tropical origin: it also warms the frozen waters of the glacial sea. The other branch, inclining towards the south, not far from the Azores, visits the coast of Africa, whence it returns to the Antilles. Throughout this vast circuit may be seen all sorts of plants and driftwood, with waifs and strays of every description borne on the bosom of the ocean. "Midway the Atlantic, in the triangular space between the Azores, Canaries, and Cape de Verd Islands, is the great Sargasso Sea, covering an area equal in extent to the Mississippi Valley: it is so thickly matted over with the Gulf Weed (Sargassum bacciferum), that the speed of vessels passing through it is actually retarded, and to the companions of Columbus it seemed to mark the limits of navigation; they became alarmed. To the eye at a little distance it seemed sufficiently substantial to walk upon." These moving vegetable masses, always green, which tail off to a steady breeze, serving as an anemometer to the mariner, afford an asylum to multitudes of mollusks and crustaceans.

The Gulf Stream plays a grand part in the Atlantic system. It carries the tepid water of the equinoctial regions into the high latitudes; beyond the fortieth parallel the temperature is sixteen degrees Cent. Urged by the south-west winds which predominate in that zone, its tepid waters mix with those of the Northern Sea, softening the rigour of the climate in these regions. To the south of the great bank of Newfoundland, the warm current, in vast volume rushing from the Florida Straits, meets the cold currents descending from the Arctic Circle through Baffin's Bay and the Sea of Greenland, running with equal velocity towards the south. A portion of these waters reascend towards the Pole along the western coast of Greenland. It is to this conflict of the polar and equatorial waters, that the formation of the banks of Newfoundland is ascribed. Each of these great currents having unceasingly deposited the débris carried in its bosom, the bank has been thus formed bit by bit in the concourse of ages.

The difference of temperature between the Gulf Stream and the waters it traverses gives birth inevitably to tempests and cyclones. In 1780 a terrible storm ravaged the Antilles, in which twenty thousand persons perished. The ocean quitted its bed and inundated whole cities; the trunks of trees, mingled with other débris, were tossed into the air. Numerous catastrophes of this kind have earned for the Gulf Stream the title of the King of the Tempests. In consequence of the numerous nautical documents which have been placed at the command of the National Observatory of Washington, and the admirable use made of them by the late Naval Secretary and his assistants, the directions and range of these cyclones engendered by the Gulf Stream may be foreseen, and their most dangerous ravages turned aside. As an example of the utility of Dr. Maury's labours in settling the direction of storms in the traject of the Gulf Stream, we quote a well-known instance: In the month of December, 1859, the American packet San Francisco was employed as a transport to convey a regiment to California. It was overtaken by one of these sudden storms, which placed the ship and its freight in a most dangerous position. A single wave, which swept the deck, tore out the masts, stopped the engines, and washed overboard a hundred and twenty-nine persons, officers and soldiers. From that moment the unfortunate steamer floated upon the waters, a waif abandoned to the fury of the wind. The day after the disaster the San Francisco was seen in this desperate situation by a ship which reached New York, although unable to assist her. Another ship met her some days after, but, like the other, could render no assistance. When the report reached New York, two steamers were despatched to her assistance; but in what direction were they to go? what part of the ocean were they to explore? The luminaries of Washington Observatory were appealed to! Having consulted his charts as to the direction and limits of the Gulf Stream at that period of the year, Dr. Maury traced on a chart the spot to which the disabled steamer was likely to be driven by the current, and the course to be taken by the vessels sent to her assistance. The crew and passengers of the San Francisco were saved before their arrival. Three ships, which had seen their distressing situation, had been able to reach them, and the steamers sent to their assistance only arrived to witness the safety of the passengers and crew. But the point where the steamer foundered shortly after they were transferred to the rescuing ships was precisely that indicated by Dr. Maury. If the ships sent to their assistance had reached in time, the triumph of Science would have been complete.

The equinoctial currents of the Pacific are very imperfectly known. It is believed, however, that they traverse the Great Ocean in its whole length, and bifurcate opposite the Asiatic coast, where the weakest branch bends northward until it encounters the polar current from Behring's Straits, when it returns along the Mexican coast. The larger branch inclines towards the south, passing round Australia, where it is met by one or many counter currents coming from the Indian Ocean—of the complicated and dangerous nature of which both Cook and La Peyrouse speak.

The cold waters from the Antarctic Pole are carried towards the Equator by three great oceanic rivers. The first bifurcates in forty-five degrees; one portion goes round Cape Horn; the other—Humboldt's current—ascends the Chilian and Peruvian coasts up to the Equator, ameliorating the rainless climate as it goes, and making it delightful. A second great current takes the direction of the African coast, and is divided at the Cape, ascending both the east and west coasts of Africa. On either side of the warm current which escapes from the intertropical parts of the Indian Ocean, but especially along the Australian coast, a polar current wends its way from the Antarctic regions, carrying supplies of cold water to modify the climate and restore the equilibrium in that part of the world. This cold current turns at first towards the west, then towards the south in the direction of Madagascar; more to the south still it is driven back by the polar current from Cape Horn. It is thus that the warm waters from the Bay of Bengal, pressed by the Indian polar current, circulate between Africa and Australia, one lateral branch of the current sweeping along the south coast of this vast continent.

The monsoons which reign in the Indian Ocean tend still more to complicate the currents, already sufficiently intricate and confused. But it is not intended at present to occupy the reader's attention further with these questions of intricate currents.

We have already spoken of a submarine current which appears to carry the waters of the Mediterranean into the Atlantic Ocean. Its existence is in some respects established by calculations which prove that the quantity of salt water supplied by the upper current through the Straits of Gibraltar is equal to seventy-two cubic miles per annum, while the quantity of fresh water brought down by the rivers is equal to six, and the quantity lost by evaporation to twelve cubic miles per annum. This would leave an annual excess of sixty-six cubic miles, if the equilibrium was not re-established by an under current flowing into the Atlantic. This hypothesis would appear to have been confirmed by a very curious fact.

Towards the end of the seventeenth century, a Dutch brig, pursued by the French corsair Phœnix, was overhauled between Tangier and Tarifa, and seemed to be sunk by a single broadside; but, in place of foundering and going down, the brig, being freighted with a cargo of oil and alcohol, floated between the two currents, and, drifting towards the west, finally ran aground, after two or three days, in the neighbourhood of Tangier, more than twelve miles from the spot where she had disappeared under the waves. She had therefore traversed that distance, drawn by the action of the under current in a direction opposite to that of the surface current. This ascertained fact, added to some recent experiments, lend their support to the opinion which admits of the existence of an outward current through the Straits of Gibraltar. Dr. Maury quotes an extract from the "log" of Lieutenant Temple, of the United States Navy, bearing the same inference. At noon on the 8th of March, 1855, the ship Levant stood into Almeria Bay, where many ships were waiting for a chance to get westwards. Here he was told that at least a thousand sail were waiting between the bay and Gibraltar, "some of them having got as far as Malaga only to be swept back again. Indeed," he adds, "no vessel had been able to get out into the Atlantic for three months past." Supposing this current to run no faster than two knots an hour, and assuming its depth to be four hundred feet only, and its width seven miles, and that it contained the average proportion of solid matter, estimated at one-thirtieth, it appears that salt enough to make eighty-eight cubic miles of solid matter were carried into the Mediterranean in those ninety days. "Now," continues Dr. Maury, "unless there were some escape for all this solid matter which has been running into the sea, not for ninety days, but for ages, it is very clear that the Mediterranean would long ere this have been a vat of strong brine, or a bed of cubic crystals."

For the same reason, Dr. Maury considers it certain that there is an under current to the south of Cape Horn, which carries into the Pacific Ocean the overflowings of the Atlantic. In fact, the Atlantic is fed unceasingly by the Great American rivers, while the Pacific receives no important affluent, but ought to be, and is, subjected to enormous losses, in consequence of the evaporation continually taking place at the surface.

Tides.

Tides are periodical movements produced by the attraction of the sun and moon. This action, which influences the whole mass of the earth, is made manifest by the swelling movement of the waters. The attractive force exercised by the moon is three times that of the sun, in consequence of its approximation to the earth, as compared to the greater luminary.

In order to comprehend the theory of tides, we shall first consider the lunar influences, putting aside for a moment the solar action.

Fig. 5. Lunar Tides.

The attraction which the moon exercises upon any point on the earth's surface is in the inverse ratio of the square of its distance. If we draw a straight line from the moon passing through the centre of the earth, this line will meet the surface of the waters at two points diametrically opposite to each other—namely, z and n (Fig. 5); one of these points would be to the moon its zenith, the other its nadir. The point of the sea which has the moon in the zenith—namely, that above which the moon is perfectly perpendicular—will be nearest to the planet, and will consequently be more strongly attractive to the centre of the earth, while the points diametrically opposite to which the moon is the nadir will be more distant, and consequently less strongly attracted by that luminary. It follows that the waters situated directly under the moon will be attracted towards it, and form an accumulation or swelling at that point; the waters at the antipodes being less strongly attracted to the moon than to the centre of the earth, will form also a secondary swelling on the surface of the sea, thus forming a double tide, accumulating at the point nearest the moon and at its antipodes. At the intermediate points of the circumference of the globe, where the waters are not subjected to the direct attraction of the moon, the sea is at low water, as represented in Fig. 5.

The earth, in its movement of rotation, presents, in the course of twenty-four hours, every meridian on its surface to the lunar attraction; consequently, each point in its turn, and at intervals of six hours, is either under the moon, or ninety degrees removed from it: it follows, that in the space of a lunar day—that is to say, in the time which passes between two successive passages of the moon on the same meridian—the oceanic waters will be at high and low tide twice in the month on every point of the surface of the globe. But this result of attraction is not exercised instantaneously. The moon has passed from the meridian of the spot before the waters have attained their greatest height; the flux reaches its maximum about three hours after the moon has culminated; and the watery mountain follows the moon all round the globe, from east to west, about three hours in its rear.

It is obvious, however, that the great inequalities of the bottom of the sea; the existence of continents; the slopes of the coast, more or less steep; the different breadths of channels and straits; finally, the winds, the pelagic currents, and a crowd of local circumstances,—must materially modify the course of the tides. Nor is the moon the only celestial body which influences the rise and fall of the waters of the sea. We have already said that the sun asserts an influence on the waves. It is true that, in consequence of its great distance, this only amounts to a thirty-eight-hundredth part of that of the earth's satellite. The inequality which exists between the solar and lunar days—the latter exceeding the first by fifty-four minutes—has also the effect of adding to or subtracting from this force alternately. When the sun and moon are in conjunction (Fig. 6), or in opposition, that is to say, placed upon the same right line, their attraction on the sea is combined, and a spring tide is produced. This happens at the period of the syzygies—the period of new and full moon. At the period of the quadrature, or the first and last quarters, the solar action, being opposed to that of lunar attraction, tends to produce a sensibly weaker tide.

Fig. 6. Lunar-Solar Tides.

These effects are never produced instantaneously; but, the impulse once given, it will continue to influence the tides for two or three days, the highest and lowest tides being nearly in the proportion of 138 to 63, or of 7 to 3. The highest tides occur at the equinoxes, when the moon is in perigee; the lowest at the solstices, when it is in apogee. In our ports, and along the coast, the water rises twice in twenty-four hours, when it is said to be high water; when it retires, it is low water: they are respectively the flux and reflux of the waves.

The tide is retarded every day about fifty minutes, the lunar day being twenty-four hours fifty minutes of mean time. If, for instance, it is high water to-day at two o'clock in the morning, that of the next day will take place at fifty minutes past two. Low water does not occur, however, at the half of the intermediate time; the flux is more rapid than the reflux: thus at Havre, Boulogne, and at corresponding places on this side of the Channel, it takes two hours and eight minutes more in retiring; at Brest, the difference is only sixteen minutes more than the flux. The daily retardation of high water by the passage of the moon in the meridian, at the equinoxes, is a constant quantity for the same locality, which can be determined by direct observation.

The height of the tide varies in the different regions of the globe, according to local circumstances. The eastern coast of Asia and the western coast of Europe are exposed to extremely high tides; while in the South Sea Islands, where they are very regular, they scarcely reach the height of twenty inches. On the western coast of South America, the tides rarely reach three yards; on the western coast of India they reach the height of six or seven; and in the Gulf of Cambay it ranges from five to six fathoms. This great difference makes itself felt in our own and adjoining countries: thus, the tide, which at Cherbourg is seven and eight yards high, attains the height of fourteen yards at Saint Malo, while it reaches the height of ten yards at Swansea, at the mouth of the Bristol Channel, increasing to double that height at Chepstow, higher up the river. In general, the tide is higher at the bottom of a gulf than at its mouth.

The highest tide which is known occurs in the Bay of Fundy, which opens up to the south of the isthmus uniting Nova Scotia and New Brunswick. There the tide reaches forty, fifty, and even sixty feet, while it only attains the height of seven or eight in the bay to the north of the same isthmus. It is related that a ship was cast ashore upon a rock during the night, so high, that at daybreak the crew found themselves and their ship suspended in mid-air far above the water!

In the Mediterranean, which only communicates with the ocean by a narrow channel, the phenomenon of tides is scarcely felt, and from this cause—that the moon acts at the same time upon its whole surface, which are not sufficiently abundant to increase the swelling mass of waters formed by the moon's attraction; consequently, the swelling remains scarcely perceptible. This is the reason why neither the Black Sea or White Sea presents a tide, and the Mediterranean a very inconsiderable one. Nevertheless, at Alexandria the tide rises twenty inches, and at Venice this height is increased to about six feet and a half. Lake Michigan is slightly affected by the lunar attraction.

Professor Whewell has prepared maps, in which the course of the tidal wave is traced in every country of the globe. We see here that it traverses the Atlantic, from the fiftieth degree of south latitude up to the fiftieth parallel north, at the rate of five hundred and sixty miles an hour. But the rapidity with which it proceeds is least in shallow water. In the North Sea it travels at the rate of a hundred and eighty miles. The tidal wave which proceeds round the coast of Scotland traverses the German Ocean and meets in St. George's Channel, between England and Ireland, where the conflict between the two opposing waves presents some very complicated phenomena.

The winds, again, exercise a great influence on the height of the tides. When the impulse of the wind is added to that of the attracting planet, the normal height of the wave is considerably increased. If the wind is contrary, the flux of the tide is almost annihilated. This happens in the Gulf of Vera Cruz, where the tide is only perceptible once in three days, when the wind blows with violence. An analogous phenomenon is observable on the coast of Tasmania.

Fig. 7. Point du Raz, Coast of Brittany.

The rising tide sometimes strikes the shore with a continuous and incredible force. This violent shock is called the surf. The swell then forms a billow, which expands to half a mile. The surf increases as it approaches the coast, when it sometimes attains the height of six or seven yards, forming an overhanging mountain of water, which gradually sinks as it rolls over itself. But this motion is not in reality progressive—it transports no floating body. The surf is very strong at the Isle of Fogo, one of the Cape de Verd Islands in the Indian Ocean, and at Sumatra, where the surf renders it dangerous and sometimes impossible to land on the coast. Fig. 7 represents the effects of the surf at Point du Raz, on the coast of Brittany. The winds adding their influence to these causes, give birth on the surface of the sea to waves or billows, which increase rapidly, rising in foaming mountains, rolling, bounding, and breaking one against the other. "In one moment," says Malte Brun, "the waves seem to carry sea-goddesses on its breast, which seem to revel amid plays and dances; in the next instant, a tempest rising out of them, seems to be animated by its fury. They seem to swell with passion, and we think we see in them marine monsters which are prepared for war. A strong, constant, and equal wind produces long swelling billows, which, rising on the same line, advance with a uniform movement, one after the other, precipitating themselves upon the coast. Sometimes these billows are suspended by the wind or arrested by some current, thus forming, as it were, a liquid wall. In this position, unhappy is the daring navigator who is subjected to its fury." The highest waves are those which prevail in the offing off the Cape of Good Hope at the period of high tide, under the influence of a strong north-west wind, which has traversed the South Atlantic, pressing its waters towards the Cape. "The billows there lift themselves up in long ridges," says Dr. Maury, "with deep hollows between them. They run high and fast, tossing their white caps aloft in the air, looking like the green hills of a rolling prairie capped with snow, and chasing each other in sport. Still, their march is stately, and their roll majestic. The scenery among them is grand. Many an Australian-bound trader, after doubling the Cape, finds herself followed for weeks at a time by these magnificent rolling swells, furiously driven and lashed by the "brave west winds." These billows are said to attain the height of thirty, and even forty feet; but no very exact measurement of the height of waves is recorded. One of these mountain waves placed between two ships conceals each of them from the other—an effect which is partially represented in Fig. 8. In rounding Cape Horn, waves are encountered from twenty to thirty feet high; but in the Channel they rarely exceed the height of nine or ten feet, except when they come in contact with some powerful resisting obstacle. Thus, when billows are dashed violently against the Eddystone Lighthouse, the spray goes right over the building, which stands a hundred and thirty feet above the sea, and falls in torrents on the roof. After the storm of Barbadoes in 1780, some old guns were found on the shore, which had been thrown up from the bottom of the sea by the force of the tempests.

Fig. 8. Height of Waves off the Cape of Good Hope.

If the waves, in their reflux, meet with obstacles, whirlpools and whirlwinds are the result—the former the terror of navigators. Such are the whirlpools known in the Straits of Messina, between the rocks of Charybdis and Scylla, celebrated as the terror of ancient mariners, and which were sung by Homer, Ovid, and Virgil:—

"Scylla latus dextrum, lævum irrequieta Charybdis,

Infestat; vorat hæc raptis revomitque carinas.

. . . Incidit in Scyllam, cupiens vitare Charybdim."

These rocks are better understood, and less redoubted in our days. At Charybdis, there is a foaming whirlpool; at Scylla, the waves dash against the low wall of rock which forms the promontory, scarcely noticed by the navigator of our days.

Another celebrated whirlpool is that of Euripus, near the Island of Eubœa; another is known in the Gulf of Bothnia. But perhaps the best known rocky danger is the Maelström, whose waters have a gyratory movement, producing a whirlpool at certain states of the tide, the result of opposing currents, which change every six hours, and which, from its power and magnitude, is capable of attracting and engulfing ships to their destruction, although chiefly dangerous to smaller craft.

To the combined effects of tides and whirlpools may also be attributed the hurricanes, so dreaded by navigators, which so frequently visit the Mauritius and other parts of the Indian Ocean. In periods of the utmost calms, when there is scarcely a breath to ruffle the air, these shores are sometimes visited by immense waves, accompanied by whirlwinds, which seem capable of blowing the ships out of the water, seizing them by the keel, whirling them round on an axis, and finally capsizing them. "At the period of the changing monsoon, the winds, breaking loose from their controlling forces, seem to rage with a fury capable of breaking up the very fountains of the deep."

The hurricanes of the Atlantic occur in the months of August and September, while the south-west monsoon of Africa and the southeast monsoon of the West Indies are at their height; the agents of the one drawing the north-east trade-winds into the interior of Mexico and Texas, the other drawing them into the interior of Africa, greatly disturbing the equilibrium of the atmosphere.

The Polar Seas.

The extreme columns of the known world are Mount Parry, situated at eight degrees from the North Pole, and Mount Ross, twelve degrees from the South Pole. Beyond these limits our maps are mute; a blank space marks each extremity of the terrestrial axis. Will man ever succeed in passing these icy barriers? Will he ever justify the prediction of the poet Seneca, who tells us that "the time will come in the distant future when Ocean will relax her hold on the world, when the immense earth will be open, when Tethys will appear amid new orbs, and where Thule (Iceland) shall no longer be the extreme limit of the earth?"

"Venient annis

Sæcula seris quibus oceanus

Vincula rerum laxet et ingens

Pateat tellus, Tethysque novos

Detegat orbes, nec sit terris

Ultime Thule."Medea.

No one can say. Every step we have taken in order to approach the Pole has been dearly purchased; and it is not without reason that navigators have named the south point of Greenland, Cape Farewell. Of the number of expeditions, for the most part English, which have been fitted out, at the cost of nearly a million sterling, to explore the Frozen Ocean, one-twentieth have had for their mission to ascertain the fate of the lamented Sir John Franklin.

The first navigator who penetrated to Arctic polar regions was Sebastian Cabot, who in 1498 sought a north-west passage from Europe to China and the Indies. Considering the date, and the state of navigation at that period, this was perhaps the boldest attempt on record. Scandinavian traditions attribute similar undertakings to the son of the King Rodian, who lived in the seventh century; to Osher, the Norwegian, in 873; and to the Princes Harold and Magnus, in 1150.

Sebastian Cabot reached as high as Hudson's Bay, but a mutiny of his sailors forced him to retrace his steps. In 1500, Gaspard de Cortereal discovered Labrador; in 1553, Sir Hugh Willoughby Nova Zembla; and Chancellor the White Sea, about the same time. Davis visited in 1585 the west coast of Greenland, and two years later he discovered the strait which bears his name. In 1596 Barentz discovered Spitzbergen, which was again seen by Hendrich Hudson, who sailed up to and beyond the eighty-second parallel. Three years later Hudson gave his name to the great Labrador Bay, but he could get no farther. His crew also revolted, and he was left in the ship's launch with his son, seven sailors, and the carpenter, who remained faithful. Thus perished one of our greatest navigators.

The Island of Jan Mayen was discovered in 1611; the channel which Baffin took for a bay, and which bears his name, was discovered in 1616. Behring discovered, in his first voyage in 1727, the strait which separates Siberia from America; he sailed through it in 1741, but his ship was stranded, and he himself died of scorbutic disease.

In the year 1771 the Polar Sea was discovered by Hearne, a fur merchant; it was explored long after by Mackenzie.

From the year 1810, when Sir John Ross, Franklin, and Parry turned their attention to the Arctic regions, these expeditions to the Polar Seas rapidly succeeded each other. In 1827 Parry reached the eighty-second degree of north latitude; and in 1845 Sir John Franklin, with the ships Erebus and Terror, and their crews, departed on their last voyage, from which neither he nor his companions ever returned. There is now no doubt that they perished miserably, after having discovered the north-west passage, which Captain M'Clure also discovered, coming from the opposite direction, in 1850. In 1855 the expedition of Dr. Elisha Kane found the sea open from the Pole.

The Antarctic Pole had in the meantime attracted the attention of navigators. In 1772 the Dutch captain, Kerguelen, discovered an island which he took for a continent. In 1774 Captain Cook explored these regions up to the seventy-first degree of latitude. James Weddell, in a small whaler, sailed past this parallel in 1823. Biscoe discovered Enderby's Land in 1831. The Zelée and Astrolabe, under the command of Captain Dumont D'Urville, of the French Marine, and the American expedition, under Captain Wilkes, reached the same region in 1838. The former discovered Adelia's Land. Finally, in 1841, Sir James Clark Ross, nephew of Sir John Ross, with the Erebus and Terror, penetrated up to the seventy-eighth degree south latitude. Here he discovered the volcanic islands which he named after his ships, and, farther to the south, a new continent or land, which he called Victoria's Land.

While these efforts were being made to penetrate the ice which surrounds the Antarctic Pole, a region having little which could attract human enterprise, the interests of commerce seemed to call for obstinate and persevering attempts to penetrate to the Arctic Pole. In spite of these numerous expeditions, however, which extend over two centuries, the regions round the North Pole are far from being known to geographers. The fogs and snows which almost always cover them were the source of many errors made by the earlier navigators. In his first voyage, made in 1818, Sir John Ross was led to think that Lancaster Sound was closed by a chain of mountains, which he called the Croker Mountains; but in the following year Captain Parry, in command of two ships, the Hecla and Griper, discovered that this was an error. This celebrated navigator discovered Barrow's Straits, Wellington Channel, and Prince Regent Inlet; Cornwallis, Sir Byam Martin, and Melville Islands, to which the name of Parry's Archipelago has been given. In this short voyage he gathered more new results than were obtained by his successors during the next forty years. He was the first to traverse these seas. Upon Sir Byam Martin Island he has described the ruins of some ancient habitations of the Esquimaux. He passed the winter on Melville Island. In order to attain his chosen anchorage in Winter's Bay, he was compelled to saw a passage in the ice of a league in length, which involved the labour of three days; but scarcely were they moored in their chosen harbour than the thermometer fell to eighteen degrees below zero. They carried ashore the ship's boats, the cables, the sails, and log-books. The masts were struck to the maintop; the rest of the rigging served to form a roof, sloping to the gunwale, with a thick covering of sail-cloth, which formed an admirable shelter from the wind and snow. Numberless precautions were taken against cold and wet under the decks. Stoves and other contrivances maintained a supportable degree of temperature. In each dormitory a false ceiling of impermeable cloth interposed to prevent the collection of moisture on the wooden walls of the ship. The crew were divided into companies, each company being under the charge of an officer, charged with the daily inspection of their clothes and cleanliness—an essential protection against scurvy. As a measure of precaution, Captain Parry reduced by one-third the ordinary ration of bread; beer and wine were substituted for spirits; and citron and lemon drinks were served out daily to the sailors. Game was sometimes substituted to vary a repast worthy of Spartans. As a remedy against ennui, a theatre was fitted up and comedies acted, for which occasions Parry himself composed a vaudeville, entitled "The North-west Passage; or, the End of the Voyage." During this long night of eighty-four days, the thermometer in the saloons marked 28°, and outside 35° below zero, and for a few minutes actually reached 47°. Some of the sailors had their members frozen, from which they never quite recovered. One day the hut which served as an observatory was discovered to be on fire. A sailor who saved one of the precious instruments lost his hands in the effort; they were completely frost-bitten in the attempt.

Nevertheless, the month of June arrived, and with it the opportunity of making excursions in the neighbourhood. It was found that, in Melville Island, the earth was carpeted with moss and herbage, with saxifrages and poppies. Hares, reindeer, the musk-ox, northern geese, plovers, white wolves and foxes, roamed around their haunts, disputing their booty with the crew. Captain Parry could not risk a second winter in this terrible region. He returned home as soon as the thaw left the passage open.

In 1821, Captain Parry undertook a second voyage with the Fury and Hecla. He visited Hudson's Bay and Fox's Channel. In his third voyage, undertaken in 1824, he was surprised by the frost in Prince Regent's Channel, and was constrained to pass the winter there. The Fury was dismantled, and, being found unfit for service, Captain Parry was obliged to abandon her and return to England.

Accompanied by Sir James Ross, Parry again put to sea in the Hecla, in April, 1826. On his third voyage, on leaving Table Island on the north of Spitzbergen, Parry placed his crew in the two training ships, Enterprise and Endeavour; the first under his own command, the second under orders of Sir James Ross. Sometimes they sailed, sometimes hauled through the crust of the ice; sometimes the ice, which pierced their shoes, showed itself bristling with points, intersected into valleys and little hills, which it was difficult to scale. In spite of the courage and energy of their crews, the two ships scarcely advanced four miles a day, while the drifting of the ice towards the south led them imperceptibly towards their point of departure. They reached latitude eighty-two degrees forty-five minutes fifteen seconds, however, and this was the extreme point which they attained.

In the month of May, 1829, Sir John Ross, accompanied by his nephew, James Clark Ross, again turned towards the Polar Seas. He entered Prince Regent's Channel, and there he found the Fury, which had been dismantled and abandoned by Parry, in these regions, eight years before. The provisions, which the old ship still contained, were quite a providential resource to Ross's crews. The distinguished navigator explored the Boothian Peninsula, and passed four years consecutively in Port Felix, without being able to disengage his vessel, the Victory. This gave him ample leisure to become familiar with the Esquimaux. Sir John Ross, in his account of this long sojourn in polar countries, has recorded many conversations with the natives, which our space does not permit us to quote. From this terrible position he was extricated, and emerged with his crew from this icy prison, when all hope of his return had been abandoned. After being exposed to a thousand dangers, Ross and his crew were at last observed by a whaling ship, which received them on board, after many efforts to attract attention. On learning that the ship which had saved them was the Isabella, formerly commanded by Captain Ross, he made himself known. "But Captain Ross has been dead two years," was the reply.

We need not repeat here the enthusiastic reception Captain Ross and his companions met with on their arrival in London.

During an excursion made by the nephew of the Commander (afterwards Sir James Clark Ross), he very closely approached the North Magnetic Pole. This was at eight o'clock on the morning of the 1st of June, 1831, on the west coast of Boothia. The dip of the magnetic needle was nearly vertical, being eighty-nine degrees fifty-nine seconds—one minute short of ninety degrees. The site was a low flat shore, rising into ridges from fifty to sixty feet high, and about a mile inland.

Contrary to the judgment of many officers of experience in polar explorations, the last and most fatal of all the expeditions was undertaken by Sir John Franklin, with one hundred and thirty-seven picked officers and men, in the ships Erebus and Terror. The adventurers left Sheerness on the 26th of May, 1846, the ships having been strengthened in every conceivable way, and found in everything calculated to secure the safety of the expedition. On the 22nd of July the ships were spoken by the whaler Enterprise, and, four days later, they were sighted by the Prince of Wales, of Hull, moored to an iceberg, waiting an opening to enter Lancaster Sound. There the veil dropped over the ships and their unhappy crews. In 1848, their fate began to excite a lively interest in the public mind. Expedition in search of them succeeded expedition, at immense cost, sent both by the English and American authorities, and by Lady Franklin herself, some of which penetrated the Polar Seas through Behring's Straits, while the majority took Baffin's Bay. In 1850, Captains Ommaney and Penny discovered, at the entrance of Wellington Channel, some vestiges of Franklin, which led to another expedition in 1857, which was got up by private enterprise, of which Captain M'Clintock had the command. Guided by the indications collected in the previous expedition, and intelligence gathered from the Esquimaux by Dr. Rae in his land expedition, Captain M'Clintock in the yacht Fox discovered, on the 6th of May, 1859, upon the north point of King William's Land, a cairn or heap of stones. Several leaves of parchment, which were buried under the stones, bearing date the 28th of April, 1848, solved the fatal enigma. The first, dated the 24th of May, 1847, gave some details ending with "all well." The papers had been dug up twelve months later to record the death of Franklin, on the 11th of June, 1847. The survivors are supposed to have been on their way to the mouth of the River Back, but they must have sunk under the terrible hardships to which they were exposed, in addition to cold and hunger.

In September, 1859, Captain M'Clintock returned to England, bringing with him many relics of our lost countrymen, found in the theatre of their misfortunes.

It only remains to us to say a few words on the latest voyages undertaken in the Polar Seas. After the return of Captain M'Clintock, in 1850, Captain M'Clure, leaving Behring's Straits, discovered the north-west passage between Melville and Baring's Island, which passage had been sought for without success during so many ages. He saw the thermometer descend fifty degrees below zero. In the month of October, 1854, he returned to England, and at a subsequent period it was ascertained with certainty that, before his death, Franklin knew of the other passage which exists to the north of America, to the south of Victoria Land, and Wollaston.

The expedition of Dr. Kane entered Smith's Strait in 1853, and advanced towards the north upon sledges drawn by dogs; the mean temperature, which ranged between thirty degrees and forty degrees below zero, fell at last to fifty degrees. At eleven degrees from the Pole they found two Esquimaux villages, called Etah and Peterovik, then an immense glacier. A detachment, conducted by Lieutenant Morton, discovered, beyond the eightieth degree of latitude, an open channel inhabited by innumerable swarms of birds, consisting of swallows, ducks, and gulls, which delighted them by their shrill, piercing cries. Seals (phoca) enjoyed themselves on the floating ice. In ascending the banks, they met with flowering plants, such as Lychnis, Hesperis, &c. On the 24th of June, Morton hoisted the flag of the Antarctic, which had before this seen the ice of the South Pole, on Cape Independence, situated beyond eighty-one degrees. To the north stretched the open sea. On the left was the western bank of the Kennedy Channel, which seemed to terminate in a chain of mountains, the principal peak rising from nine thousand to ten thousand feet, which was named Mount Parry. The expedition returned towards the south, and reached the port of Uppernavick exhausted with hunger, where it was received on board an American ship. Dr. Kane, weakened by his sufferings, from which he never quite recovered, died in 1857.

We cannot conclude this rapid sketch of events connected with the expeditions to the Arctic Pole without noting a geological fact of great and singular interest. When opportunities have presented themselves of examining the rocks in the regions adjoining the North Pole, it has been found that great numbers belong to the coal measures. Such is the case in Melville Island and Prince Patrick's Island. Under the ice which covers the soil in these islands coal exists, with all the fossil vegetable débris which invariably accompany it. This shows that in the coal period of geology, the North Pole was covered with the rich and abundant vegetation whose remains constitute the coal-fields of the present day; and proves to demonstration that the temperature of these regions was, at one period of the earth's history, equal to that of equatorial countries of the present day. What a wonderful change in the temperature of these regions is thus indicated! It is, indeed, a strange contrast to find coal formations under the soil covered by the polar ice. Let us suppose that human industry should dream of establishing itself in these countries, and drawing from the earth the combustible so needed to make it habitable, thus furnishing the means of overcoming the rigorous climatic conditions of these inhospitable regions.

The Antarctic Pole is probably surrounded by an icy canopy not less than two thousand five hundred miles in diameter; and numerous circumstances lead to the conclusion that the vast mass has diminished since 1774, when the region was visited by Captain Cook. The Antarctic region can only be approached during the summer, namely, in December, January, and February.

The first navigator who penetrated the Antarctic circle was the Dutch captain, Theodoric de Gheritk, whose vessel formed part of the squadron commanded by Simon de Cordes, destined for the East Indies. In January, 1600, a tempest having dispersed the squadron, Captain Gheritk was driven as far south as the sixty-fourth parallel, where he observed a coast which reminded him of Norway. It was mountainous, covered with snow, stretching from the coast to the Isles of Solomon. The report of Simon de Cordes was received with great incredulity, and the doubts raised were only dissipated when the New South Shetland Islands were definitely recognized. The idea of an Antarctic continent is, however, one of the oldest conceptions of speculative geography, and one which mariners and philosophers alike have found it most difficult to relinquish. The existence of a southern continent seemed to them to be the necessary counterpoise to the Arctic land. The Terra Australis incognita is marked on all the maps of Mercator, round the South Pole, and when the Dutch officer, Kerguelen, discovered, in 1772, the island which bears his name, he quoted this idea of Mercator as the motive which suggested the voyage. In 1774, Captain Cook ventured up to and beyond the seventy-first degree of latitude under the one hundred and ninth degree west longitude. He traversed a hundred and eighty leagues, between the fiftieth degree and sixtieth degree of south latitude, without finding the land of which mariners had spoken: this led him to conclude that mountains of ice, or the great fog-banks of the region, had been mistaken for a continent. Nevertheless, Cook clung to the idea of the existence of a southern continent. "I firmly believe," he says, "that near the Pole there is land where most part of the ice is formed which is spread over the vast Southern Ocean. I cannot believe that the ice could extend itself so far if it had not land—and I venture to say land of considerable extent—to the south. I believe, nevertheless, that the greater part of this southern continent ought to lie within the Polar Circle, where the sea is so encumbered with ice as to be unapproachable. The danger run in surveying a coast in these unknown seas is so great, that I dare to say no one will venture to go farther than I have, and that the land that lies to the south will always remain unknown. The fogs are there too dense; the snowstorms and tempests too frequent; the cold too severe; all the dangers of navigation too numerous. The appearance of the coast is the most horrible that can be imagined. The country is condemned by nature to remain unvisited by the sun, and buried under eternal hoar frost. After this report, I believe that we shall hear no more of a southern continent." This description of these desolate regions, to which the great navigator might have applied the words of Pliny, "Pars mundi a natura damnata et densa mersa caligine," only excited the courage of his successors. In our days, several expeditions have been fitted out for the express survey of regions which may be characterised as the abode of cold, silence, and death. In 1833, a free passage opened itself into the Antarctic Sea. The Scottish whaling ship, commanded by James Weddell, entered the pack ice, and penetrated it in pursuit of seals; but having, by chance, found the sea open on his course, he forced his way up to seventy-four degrees south latitude, and under the thirty-fourth degree of longitude, but the season was too advanced, and he and his crew retraced their steps. The voyage of Captain Weddell caused a great sensation, and suggested the possibility of more serious expeditions. Twelve years later three great expeditions were fitted out: one, under Dumont D'Urville, of the French Marine; an American expedition, under Captain Wilkes, of the United States Navy; and an English expedition, under Sir James Clark Ross.

Dumont D'Urville, who perished so miserably in the railway catastrophe at Versailles, in 1842, passed the Straits of Magellan on the 9th of January, 1838, having under his command the two corvettes Astrolabe and Zelée. He expected to find it as Weddell had described, and that, after passing the first icy barrier, he should find an open sea before him. But he was soon compelled to renounce this hope. The floating icebergs became more and more closely packed and dangerous. The southern icebergs do not circulate in straits and channels already formed, like those of the North Pole, but in enormous detached blocks which hug the land. Sometimes in shallow water they form belts parallel to the base of the cliffs, intersected by a small number of sinuous narrow channels. These icy cliffs present a face more or less disintegrated as they approximate to the rocky shore. The blocks of ice form at first huge prisms, or tabular, regular masses of a whitish paste; but they get used up by degrees, and rounded off and separated under the action of the waves, which chafe them, and their colour becomes more and more limpid and bluish. They ascend freely towards the north, in spite of the winds and currents which carry them in the contrary direction. One year with another these floating icebergs accumulate with very striking differences, and it is only by a rare chance that they open up a free passage such as Captain Weddell had discovered. These floating islands of ice have been met with in thirty-five degrees south latitude, and even as high as Cape Horn.

The two French ships frequently found themselves shut up in the icebergs, which continued to press upon them, and driven before the north winds, until the south wind again dispersed their vast masses, enabling them to issue from their prison in health and safety. In some cases D'Urville found it necessary to force his ship through fields of ice by which he was surrounded and imprisoned, and to cut his way by force through the accumulating blocks, using the corvette as a sort of battering-ram. In 1838 he recognized, about fifty leagues from the South Orkney Isles, a coast, to which he gave the name of Louis Philippe's and Joinville's Land. This coast is covered with enormous masses of ice, which seemed to rise to the height of two thousand six hundred feet. Ross discovered still more lofty peaks, such as Mount Penny and Mount Haddington, rising about seven thousand feet. The English navigator states that this land is only a great island. The crew of D'Urville's ship being sickly and overworked, he returned to the port of Chili, whence he again issued for the South Pole in the following January.

On this occasion his approach was made from a point diametrically opposite to the former. He very soon found himself in the middle of the ice. He discovered within the Antarctic Circle land, to which he gave the name of Adelia's Land. The long and lofty cliffs of this island or continent he describes as being surrounded by a belt of islands of ice at once numerous and threatening. D'Urville did not hesitate to navigate his corvettes through the middle of the band of enormous icebergs which seemed to guard the Pole and forbid his approach to it. For some moments his vessels were so surrounded that they had reason to fear, from moment to moment, some terrible shock, some irreparable disaster. In addition to this, the sea produces around these floating icebergs, eddies, which were not unlikely to draw on the ship to the destruction with which it was threatened at every instant. It was in passing at their base that D'Urville was able to judge of the height of these icy cliffs. "The walls of these blocks of ice," he says, "far exceed our masts and riggings in height; they overhang our ships, whose dimensions seem ridiculously curtailed. We seem to be traversing the narrow streets of some city of giants. At the foot of these gigantic monuments we perceive vast caverns hollowed by the waves, which are engulfed there with a crashing tumult. The sun darts his oblique rays upon the immense walls of ice as if it were crystal, presenting effects of light and shade truly magical and startling. From the summit of these mountains, numerous brooks, fed by the melting ice produced by the summer heat of a January sun in these regions, throw themselves in cascades into the icy sea.

"Occasionally these icebergs approach each other so as to conceal the land entirely, and we only perceive two walls of threatening ice, whose sonorous echoes send back the word of command of the officers. The corvette which followed the Astrolabe appeared so small, and its masts so slender, that the ship's crew were seized with terror. For nearly an hour we only saw vertical walls of ice." Ultimately they reached a vast basin, formed on one side by the chain of floating islands which they had traversed, and on the other by high land rising three and four thousand feet, rugged and undulating on the surface, but clothed over all with an icy mantle, which was rendered dazzlingly imposing in its whiteness by the rays of the sun. The officers could only advance by the ship's boats through a labyrinth of icebergs up to a little islet lying opposite to the coast. They touched the land at this islet; the French flag was planted, possession was taken of the new continent, and, in proof of possession, some portions of rock were torn from the scarped and denuded cliffs. These rocks are composed of quartzite and gneiss. The southern continent, therefore, belongs to the primitive formation, while the northern region belongs in great part to the transition, or coal formation. According to the map of Adelia's Land, traced by D'Urville over an extent of thirty leagues of country, the region is one of death and desolation, without any trace of vegetation.

A little more to the north, the French navigator had a vague vision on the white lines of the horizon of another land, which he named Côte Clarie, or Coast Clear, the existence of which was soon confirmed by the American expedition under Commodore Wilkes. This officer has explored the southern land on a larger scale than any other navigator, but he suffered himself to be led into error by the dense fogs of the region, and has laid down coast lines on his map where Sir James Boss subsequently found only open sea—an error which has very unjustly thrown discredit on the whole expedition.

The English expedition entered this region on Christmas Day, 1840, which was passed by Ross in a strong gale, with constant snow or rain. Soon after, the first icebergs were seen, having flat tabular summits, in some instances two miles in circumference, bounded on all sides by perpendicular cliffs. On New Year's Day, 1841, the ships crossed the Antarctic Circle, and reached the edge of the pack ice, which they entered, after skirting it for several days. On the 5th, the pack was passed through, amid blinding snow and thick fog, which on clearing away revealed an open sea, and on the 11th of January land was seen directly ahead of the ships. A coast line rose in lofty snow-covered peaks at a great distance. On a nearer view, this coast is thus described: "It was a beautifully clear evening, and two magnificent ranges of mountains rose to elevations varying from seven thousand to ten thousand feet above the level of the sea." The glaciers which filled their intervening valleys, and which descended from near the mountain summits, projected in many places several miles into the sea, and terminated in lofty perpendicular cliffs. In a few places the rocks broke through their icy covering, by which alone we could be assured that lava formed the nucleus of this, to all appearance, enormous iceberg. This antarctic land was named Victoria Land, in honour of the Queen. It was coasted up to latitude seventy-eight degrees south, and near to this a magnificent volcanic mountain presented itself, rising twelve thousand feet above the level of the sea, which emitted flame and smoke in splendid profusion. The flanks of this gigantic mountain were clothed with snow almost to the mouth of the crater from which the flaming smoke issued. At a short distance, Ross discovered the cone of an extinct, or, at least, inactive volcano nearly as lofty. He gave to these two volcanoes the names of his vessels, Erebus and Terror (Fig. 9)—names perfectly in harmony with the surrounding desolation. The ice-covered cliffs rose about a hundred and ninety feet high, and appear to be about three hundred feet deep, soundings being found at about four hundred fathoms. In the distance, towards the south, a range of lofty mountains were observed, which Ross named Mount Parry, in honour of his old commander. When Ross retraced his steps, the expedition had advanced as far as the seventy-ninth degree of south latitude.

Fig. 9. Mounts Erebus and Terror.

It may be said of polar countries, that they form a transition state between land and sea, for water is always present, although in a solid state; the surface is always at a very low temperature; snow does not melt as it falls, and the sea is thus sometimes covered with a continuous sheet of frozen snow; sometimes with enormous floating blocks of ice which are driven by the currents. Meeting with these floating masses of ice is one of the dangers of polar navigation. Captain Scoresby has given a very detailed description of the different kinds of ice met with in the Arctic Seas. The ice-fields of this writer form extensive masses of solid water, of which the eye cannot trace the limits, some of them being thirty-five leagues in length and ten broad, with a thickness of seven to eight fathoms; but generally these ice-fields rise only four to six feet above the water, and reach from three to four fathoms beneath the surface. Scoresby has seen these ice-fields forming in the open sea. When the first crystals appear, the surface of the ocean is cold enough to prevent snow from melting as it falls. On the approach of congelation the surface solidifies, and seems as if covered with oil; small circles are formed, which press against each other, and are finally soldered together until they form a vast field of ice, the thickness of which increases from the lower surface.

The water produced from melted ice is perfectly fresh—the result of a well-known physical cause. When a saline solution like sea water is congealed by cold, pure water alone passes into the solid state, the saline solution becomes more concentrated, increases in density, and, sinking to the bottom, remains liquid. Blocks of ice, therefore, in the Polar Seas, are always available for domestic use. There are, however, salt blocks of ice, which are distinguished from fresh-water ice by their opaqueness and their dazzling white colour: this saltness is due to the sea water retained in its interstices. Scoresby amused himself sometimes by shaping lenses of ice, with which he is said to have set fire to gunpowder, much to the astonishment of his crew.

The ice-fields, which are formed in higher latitudes, are driven towards the south by winds and currents, but sooner or later the action of the waves breaks them up into fragments. The edges of the broken icebergs are thus often rising and continually changing: these asperities and protuberances are called hummocks by English navigators; they give to the polar ice an odd, irregular appearance. Hummocks form themselves of the stray, broken icebergs which come in contact with each other at their edges, and thus form vast rafts, the pieces of which may exceed a hundred yards in length.

When these icebergs are separated by open spaces, through which vessels can be navigated, the pack ice is said to be open. But it often happens that mountains of ice occur partly submerged, where one edge is retained under the principal mass, while the other is above the water. Scoresby once passed over a calf, as English mariners call these icy mountains, but he trembled while he did so, dreading lest it should throw his vessel, himself, and crew into the air before he could pass it. The aspect of the ice-fields varies in a thousand ways. Here it is an incoherent chaos resembling some volcanic rocks, with crevices in all directions, bristling with unshapely blocks piled up at random; there it is a strongly-marked plain, an immense mosaic formed of vast blocks of ice of every age and thickness, the divisions of which are marked by long ridges of the most irregular forms; sometimes resembling walls composed of great rectangular blocks, sometimes resembling chains of hills, with great rounded summits.

In the spring, when a thaw sets in, and the fields begin to break up, the pieces of light ice which unite the great blocks into unique masses are the first to melt; the several blocks then separate, and the motion of the water soon disperses them, and the imprisoned ships find a free passage. But a day of calm is still sufficient to unite the dispersed masses, which oscillate and grind against each other with a strange noise, which sailors compare to the yelping of young dogs.

When a ship is shut up in one of these floating ice-fields, inexplicable changes sometimes occur in the vast incoherent aggregations. Vessels, which think themselves immovable, are found in a few hours to have completely reversed their positions. Two ships shut in at a short distance from each other were driven many leagues without being able to perceive any change in the surrounding ice. At other times ships are drawn with the floating ice-fields, like the white bears, who make long voyages at sea upon these monster vehicles. In 1777 the Dutch vessel, the Wilhelmina, was driven with some other whaling ships from eighty degrees north back to sixty-two degrees, in sight of the Iceland coast. During this terrible journey the ships were broken up one after the other. More than two hundred persons perished, and the remainder reached land with difficulty.

Lieutenant De Haven, navigating in search of Sir John Franklin, was caught in the ice in the middle of the channel in Wellington Strait. During the nine months which he remained in captivity, he drifted nearly thirteen hundred miles towards the south; and the ship Resolute, abandoned by Captain Kellet in an ice-field of immense extent, was drifted towards the south with this vast mass to a much greater distance.

Some curious speculations are hazarded by Dr. Maury, arising out of his investigations of winds and currents, facts being revealed which indicate the existence of a climate, mild by comparison, within the Antarctic Circle. These indications are a low barometer, a high degree of aerial rarefaction, and strong winds from the north. "The winds," he says, "were the first to whisper of this strange state of things, and to intimate to us that the Antarctic climates are in winter very unlike the Arctic for rigour and severity." The result of an immense mass of observation on the polar and equatorial winds reveals a marked difference in atmospherical movements north, as compared with the same movements south of the Equator; the equatorial winds of the northern hemisphere being only in excess between the tenth and thirteenth parallel, while those of the southern hemisphere are dominant over a zone of forty-five degrees, or from thirty-five degrees south to ten degrees north.

"The fact that the influence of the polar indraught upon the winds should extend from the Antarctic to the parallel of forty degrees south, while that from the Arctic is so feeble as scarcely to be felt in fifty degrees north, is indicative enough as to the difference in degree of aerial rarefaction over the two regions. The significance of the fact is enhanced by the consideration that the 'brave west winds,' which are bound to the place of greatest rarefaction, rush more violently and constantly along to their destination than do the counter-trades of the northern hemisphere. Why should these polar-bound winds differ so much in strength and prevalence, unless there be a much more abundant supply of caloric, and, consequently, a higher degree of rarefaction, at one pole than at the other?"

That this is the case is confirmed by all known barometrical observations, which are very much lower in the Antarctic than in the Arctic, and Dr. Maury thinks this is doubtless due to the excess in Antarctic regions of aqueous vapour and this latent heat.

"There is rarefaction in the Arctic regions. The winds show it, the barometer attests it, and the fact is consistent with the Russian theory of a Polynia in polar waters. Within the Antarctic Circle, on the contrary, the winds bring air which has come over the water for the distance of hundreds of leagues all around; consequently, a large portion of atmospheric air is driven away from the austral regions by the force of vapour."

CHAPTER III.

LIFE IN THE OCEAN.

"See what a lovely shell, small and pure as a pearl,

Frail, but a work divine, made so fairly well,

With delicate spore and whorl, a miracle of design." Tennyson.

"The appearance of the open sea," says Frédol, from whose elegant work this chapter is chiefly compiled, "far from the shore—the boundless ocean—is to the man who loves to create a world of his own, in which he can freely exercise his thoughts, filled with sublime ideas of the Infinite. His searching eye rests upon the far-distant horizon. He sees there the ocean and the heavens meeting in a vapoury outline, where the stars ascend and descend, appear and disappear in their turn. Presently this everlasting change in nature awakens in him a vague feeling of that sadness 'which,' says Humboldt, 'lies at the root of all our heartfelt joys.'"

Emotions of another kind and equally serious are produced by the contemplation and study of the habits of the innumerable organized beings which inhabit the great deep. In fact, that immense expanse of water, which we call the sea, is no vast liquid desert; life dwells in its bosom as it does on dry land. Here this mystery reigns supreme in the midst of its expansions, luxuries, and agitations. It pleases the Creator. It is the most beautiful, the most brilliant, the noblest, and the most incomprehensible of His manifestations. Without life, the world would be as nothing. The beings endowed with it transmit it faithfully to other beings, their children, and their successors, which will be, like them, the depositaries of the same mysterious gift; the marvellous heritage thus traverses years and hundreds of years without losing its powers; the globe is redolent with the life which has been so bounteously distributed over it. In the words of Lamartine, "We know what produces life, but we know not what it is;" and this ignorance is perhaps the powerful attraction which provokes our curiosity and excites us to study.

Every living being is animated by two principles, between which a silent but incessant combat is being carried on—life, which assimilates, and death, which disintegrates. At first, life is all powerful—it lords it over matter; but its reign is limited. Beyond a certain point its vigour is gradually impaired; with old age it decays; and is finally extinguished with time, when the chemical and physical laws seize upon it, and its organization is destroyed. But the elements, though inert at first, are soon reanimated and occupied with a new life. Every plant, every animal is bound up with the past, and is part of the future, for every generation which starts into life is only the corollary upon that which expires, and the prelude of another which is about to be born. Life is the school of death; death is the foster-mother of life.

Life, however, does not always exhibit itself at the moment of its formation. It is visible later, and only after other phenomena. In order to develope itself, a suitable soil or other medium must be prepared, and other determinate physical and chemical conditions provided. The presence and diffusion of living beings are no chance products; they follow rigorously an order of law. Speaking of the higher forms of animal life, the Duke of Argyll says, in his able and satisfactory work, "The Reign of Law,"—"In all these there is an observed order in the most rigid scientific sense, that is, phenomena in uniform connexion and mutual relations which can be made, and are made, the basis of systematic classification. These classifications are imperfect, not because they are founded on ideal connexions where none exist, but only because they fail in representing adequately the subtle and pervading order which binds together all living things."

The knowledge of fossils has thrown great light upon the regular and progressive development of organization. The evolution of living beings seems to have commenced with the more rudimentary forms; the more ancient rocks, until very recently, had revealed no traces of life, and what has been revealed tends to confirm this view. In the Cambrian rocks of Bray Head, county Wicklow, the Oldhamia is a zoophyte of the simplest organization, and the Rhizapods found near the bottom of the Azoic rocks of Canada are the lowest form of living types; and it is only in beds of comparatively recent formation that complex organization exists. Vegetables first show themselves, and even among these the simplest forms have priority. Animals afterwards appear, which, as we have seen, belong to the least perfect classes. The combinations of life, at first simple, have become more and more complex, until the creation of man, who may be considered the masterpiece of organization.

If we expose a certain quantity of pure water to the light and air in the spring, we should soon see it producing shades of a yellowish or greenish colour. These spots, examined through the microscope, reveal thousands of vegetable agglomerates. Presently thousands of animalcules appear, which swim about among the floating masses, nourishing themselves with its substance. Other animalcules then appear, which, in their turn, pursue and devour the first.

In short, life transforms inanimate into organized matter. Vegetables appear first, then come herbivorous animals, and then come the carnivorous. Life maintains life. The death of one gives food and development to others, for all are bound up together—all assist at the metamorphoses continually occurring in the organic as in the mineral world, the result being general and profound harmony—harmony always worthy of admiration. The Creator alone is unchangeable, omnipotent, and permanent; all else is transition.

The inhabitants of the water are much more numerous than those of the solid earth. "Upon a surface less varied than we find on continents," says Humboldt, "the sea contains in its bosom an exuberance of life of which no other portion of the globe could give us any idea. It expands in the north as in the south; in the east as in the west. The seas, above all, abound with it; in the bosom of the deep, creatures corresponding and harmonizing with each other sport and play. Among these especially the naturalist finds instruction, and the philosopher subjects for meditation. The changes they undergo only impress upon our minds more and more a sentiment of thankfulness to the Author of the universe."

Yes, the ocean in its profoundest depths—its plains and its mountains, its valleys, its precipices, even in its ruins—is animated and embellished by innumerable organized beings. These are at first plants, solitary or social, erect or drooping, spreading into prairies, grouped in patches, or forming vast forests in the oceanic valleys. These submarine forests protect and nourish millions of animals which creep, which run, which swim, which sink into the sands, attach themselves to rocks, lodge themselves in crevices, which construct dwellings for themselves, which seek for or fly from each other, which pursue or fight, caress each other lovingly, or devour each other without pity. Charles Darwin truly remarks somewhere that our terrestrial forests do not maintain nearly so many living beings as those which swarm in the bosom of the sea. The ocean, which for man is the region of asphyxia and death, is for millions of animals the region of life and health: there is enjoyment for myriads in its waves; there is happiness on its banks; there is the blue above all.

The sea influences its numerous inhabitants, animal or vegetable, by its temperature, by its density, by its saltness, by its bitterness, by the never-ceasing agitation of its waves, and by the rapidity of its currents.

We have seen in preceding chapters that the sea only freezes under intense cold, and then only at the surface, and that at the depth of five hundred fathoms the same permanent temperature exists in all latitudes. On the other hand, it is agreed that the agitations produced by the most violent storms are never felt beyond the depth of twelve or thirteen fathoms. From this it follows that animals and vegetables, by descending more or less, according to the cold or disturbing movements, can always reach a medium which agrees with their constitutions.

The hosts of the sea are distinguished by a peculiar softness. Certain pelagic plants present only a very weak, feeble consistence; a great number are transformed by ebullition into a sort of jelly. The flesh of marine animals is more or less flaccid; many seem to consist of a diaphanous mucilage. The skeleton of the more perfect species is more or less flexible and cartilaginous; and it rarely attains, as to weight and consistency, the strength of bone exhibited by terrestrial vertebrate animals. Nevertheless, both the shells and coral produced in the bosom of the ocean are remarkable for their stony solidity. Among marine bodies, in short, we find at once the softest and hardest of organized substances.

The separation of organized beings, nourished by the ocean, is subjected to certain fixed laws. We never find on the coast, except by evident accident, the same species that we meet with far from the shore; nor on the surface, creatures whose habits lead them to hide in the depths of ocean. What immense varieties of size, shape, form, and colour, from the nearly invisible vegetation which serves to nourish the small zoophytes and mollusks, to the long, slender algæ of fifty—and even five hundred—yards in length! How vast the disparity between the microscopic infusoria and the gigantic whale!

"We find in the sea," says Lacepede, "unity and diversity, which constitute its beauty; grandeur and simplicity, which give it sublimity; puissance and immensity, which command our wonder."

In the following pages we shall figure and describe many inhabitants of the sea; but how many remain still to figure and describe! During more than two thousand years research has been multiplied, and succeeded by research without interruption. "But how vast the field," as Lamarck observes, "which Science has still to cultivate, in order to carry the knowledge already acquired to the degree of perfection of which it is susceptible!"

"When the tide retires from the shore, the sea leaves upon the coast some few of the numberless beings which it bears in its bosom. In the first moments of its retreat, the naturalist may collect a crowd of substances, vegetable and animal, with their various characteristic colours and properties. The inhabitants of the coast find there their food, their commerce, and their occupations. At low water the nearest villages and hamlets send their contingents, old and young, men, women, and children, to the harvest. Some apply themselves to gathering the riband seaweed (Zostera), the membranous Ulva, the sombre brown Fucus vesiculosus, formerly a source of great wealth to the dwellers by the sea, being then much used in making kelp; others gather the small shells left on the sands; boys mount upon the rocks in search of whelks (Buccinum), mussels (Mytilus), detach limpets (Patella), and other edible marine animals, from the rocks to which they have attached themselves. On some coasts, shells, as Mactra, Cytheria, and Bucardium, are sought for their beauty. By turning the stones, or by sounding the crevices of the rocks with a hook at the end of a lath, polypes and calmars are sometimes surprised—sometimes even sea and conger eels, which have sought refuge there; while the pools, left here and there by the retiring tide, are dragged by nets of very small mesh, in which the smaller crustaceous mollusks and small fish are secured."

In the Mediterranean and other inland seas, where the tide is almost inappreciable, there exist a great number of animals and vegetables belonging to the deep sea, which the waves or currents very rarely leave upon the sea shore. There are others so fugitive, or which attach themselves so firmly to the rocks, that we can watch them only in their habitats. It is necessary to study them floating on the surface of the waves, or in their mysterious retirements. Hence the necessity that naturalists should study the living productions of the salt water even in the bosom of the ocean, and not on the sea shore.

The means generally employed for this purpose is a drag-net, sounding-line, and other engines suitable for scraping the bottom, and breaking the harder rocks. In a voyage which Milne Edwards made to the coast of Sicily, he formed the idea of employing an apparatus invented by Colonel Paulin, which consisted of a metallic casque provided with a visor of glass, and consequently transparent, which fixed itself round the neck by means of a copper collar made water-tight by stuffing—a diving-bell, in short, in miniature. It communicated with an air-pump by means of a flexible tube. Four men were employed in serving the pump, two exercising it while the other two rested themselves. Other men held the extremity of a cord, which was passed over a pulley attached at a higher elevation, and enabled them to hoist up the diver with the necessary rapidity in emergencies. A vigilant observer held in his hand a small signal cord. The immersion of the diver was facilitated by heavy leaden shoes, which assisted him at the same time to maintain his vertical position at the bottom. M. Edwards made the descent with this apparatus in three fathoms water with perfect success. He was thus enabled to study, in their most hidden and most inaccessible retreats, the radiate animals, mollusks, crustaceans, and annelids, especially their larvæ and eggs, and by his descriptions to contribute most essentially to make known the functions, manners, and mode of development of certain inhabitants of the sea, whose sojourn and habits would seem to sequestrate them for ever from our observation.

Another and easier mode of studying the living creatures sheltered by the sea was first suggested by M. Charles des Moulins of Bordeaux, in 1830. The aquarium, which is charged with fresh or salt water, according to the beings it is intended to contain, serves the same purpose for the inhabitants of the deep which the aviary does for the birds of the air—cages of glass being used in place of iron wire or wicker-work, and water in place of atmospheric air.

When a globe is filled with fresh water, and with mollusks, crustaceans, or fishes, it is observed, after a few days, that the water loses its transparency and purity, and becomes slightly corrupt. It necessarily follows that the water must be changed from time to time. Changing the water, however, causes much suffering, and even death to the animals. Besides, the new water does not always present the same composition, the same aeration, or the same temperature with that which is replaced. To obviate this defect, and taking a leaf out of Nature's book, M. Moulins proposed to put into the vase a certain number of aquatic plants floating or submerged—duckweed, for example—which would act upon the water in a direction inverse to that of the animals inhabiting it. It is known that vegetables assimilate carbon, while decomposing the carbonic acid produced by the respiration of animals, thus disengaging the oxygen indispensable to animal life. In this simple manner was the necessary change of water obviated. The same happy idea has been successfully applied to salt water, and aquariums for salt-water plants and animals have been proposed on a great scale. That of the Zoological Gardens of Paris, in the Bois de Boulogne, inaugurated in 1861, is perhaps the largest in the world. It is a solid stone building of fifty yards in length by about twelve broad, presenting a range of forty reservoirs of Angers slate, running north and south. The reservoirs are nearly cubical, presenting in front the strong glass of Saint Gobain, which permits of the interior being seen. They are lighted from above; but the light is weak, greenish, uniform, and consequently mysterious and gloomy, giving a pretty exact imitation of the submarine light some fathoms down. Each reservoir contains about two hundred gallons of water. It is furnished with rocks disposed a little in the form of an amphitheatre, and in a picturesque manner. Upon the rocks various species of marine vegetables are planted. The bottom is of shingle, gravel, and sand, in order to give certain animals a sufficiently natural retreat.

Ten of these reservoirs are intended for marine animals. The water employed is never changed, but it is kept in continual agitation by circulation, produced by a current of water led from the great pipe which feeds the Bois de Boulogne. This water, being subjected to a strong pressure, compresses a certain portion of air, which, being permitted to act on a portion of the sea water contained in a closed cylinder placed below the level of the aquarium, makes it ascend, and enter with great force into a reservoir, into which it is thrown from a small jet. The sea water thus pressed absorbs a portion of the air, which is drawn with it into the reservoir. A tube placed in a corner of the reservoir receives the overflow, and conducts it into a closed carbon filter, whence it passes into a gravelly underground reservoir, returning again to the closed cylinder. The water is once more subjected to the pressure of air, and again ascends to the aquarium. The cylinder being underground, a temperature equal to about sixteen degrees Cent., which is nearly the uniform temperature of the ocean, is easily maintained. During winter, the aquarium is heated artificially.

CHAPTER IV.

ZOOPHYTES.

"Nature is nowhere more perfect than in her smaller works."

"Natura nusquam magis quàm in minimis tota est." Pliny.

It will not be out of place here to offer some remarks on animals in general, including the whole kingdom as well as the great divisions which form the subject of this particular volume. But considering the vastness of the subject, and our imperfect knowledge of the whole animal series as a subject of study, nothing is more difficult than to seize upon the real analogies between beings of types so varied,—of organizations so dissimilar. The arrangements which naturalists have established in order to study and describe animals—the divisions, classes, orders, families, genera, and species—are admirable contrivances for facilitating the study of creatures numerous as the sands of the sea shore. Without this precious means of logical distribution, the individual mind would recoil before the task of describing the innumerable phalanges of contemporary animal life. But the reader must never forget that these methodical divisions are pure fictions, due to human invention: they form no part of nature; for has not Linnæus told us that nature makes no leaps, natura non facit saltus? Nature passes in a manner almost insensibly from one stage of organization to another, altogether irrespective of human systems.

Moreover, when we come to watch the confines of the animal and vegetable kingdom, we realise how difficult it is to seize the precise line of demarcation which separates the great kingdoms of Nature. We have seen in the "Vegetable World" germs of the simplest organization, as in the Cryptogamia, spores, as in the Algæ, and fruitful corpuscles, as in the Mosses, which seem to be invested with some of the characteristics of animal life, for they appear to be gifted with organs of locomotion, namely, vibratile cilia, by means of which they execute movements which are to all appearance quite voluntary. Side by side with these are vegetable germs and fecundating corpuscles, known as antherozoides among the Algæ, Mosses, and Ferns, which, when floating in water, go and come like the inferior animals, seeking to penetrate into cavities, withdrawing themselves, returning again, and again introducing themselves, and exhibiting all the signs of an apparent effort. Let us compare the Infusoria, or even the Polypi and Gorgons, with these shifting vegetable organisms, and say if it is easy to determine, without considerable study, which is the plant and which the animal. The precise line of demarcation which it is so desirable to establish between the two kingdoms of Nature is indeed difficult to trace.

The word zoophyte, to which this comparison introduces us, seems very happily applied: it is derived from the Greek word ζῶον, animal, and φυτὸν, plant; and is, as it seems to us, quite worthy of being retained in Science, because it consecrates and materialises, so to speak, a sort of fusion between the two kingdoms of Nature at their confines. Let us guard ourselves, however, from carrying this idea too far, and, upon the faith of a happy word, altering altogether the true relations of created beings. In adopting the name zoophyte, to indicate a great division of the animal kingdom, the reader must not imagine that there is any ambiguity about the creatures designated, or that they belong at once to both kingdoms, or that they might be ranged indifferently in the one or the other. Zoophytes are animals, and nothing but animals; the justification for using a designation which signifies animal-plant is, that many of them have an exterior resemblance to plants; that they divide themselves by offshoots, as some plants do, and are sometimes crowned with organs tinted with lively colours, like some flowers.

This analogy between plants and zoophytes is nowhere more apparent than in the coral. Rooted in the soil and upon rocks, the form of its branches many times subdivided, above all, the coloured appendages which at certain periods so closely resemble the corolla of a flower, have all the form and appearance of plants. Until the eighteenth century most naturalists classed the coral as Linnæus did, without the least hesitation, with analogous creations in the vegetable world. Réaumur long contended for the contrary opinion; but it is only in our day that the animal nature of the coral is satisfactorily established. The sea anemone may be cited as another striking example of the resemblance borne by certain inferior organisms to vegetables. We hold, then, that we are justified in using the word zoophyte to designate the beings which now occupy our attention.

We shall not surprise our readers by telling them that the structure of the zoophyte, especially in its inferior orders, is excessively simple. They are the first steps in the scale of animal life, and in them a purely rudimentary organization was to be expected. In these beings—true types of animal life—the several parts of the body, in place of being disposed in pairs on each side of its longitudinal plane, as occurs in animals of a higher organization, are found to radiate habitually round an axis or central point, and this whether in its adult or juvenile state. Zoophytes have not generally an articulate skeleton, either exterior or interior, and their nervous system, where it exists, is very slightly developed. The organs of the senses, other than those of touch, are altogether absent in the greater part of beings which belong to this, the lowest class of the last division of the animal kingdom.

Several questions arise here: Has the zoophyte sentiment, feeling, perception? Has it consciousness, sense, sensibility? The question is insoluble; it is an abyss of obscurity. The coral, or rather the aggregation of living beings which bear the name, are attached to the rock which has seen their birth, and which will witness their death: the infusoria, of microscopic dimensions, which revolve perpetually in a circle infinitesimally small; the Amœbæ, the marvellous Proteus, which in the space of a minute changes its form a hundred times under theœ surprised eyes of the observer, are, in truth, mere atoms charged with life. Yet all these beings have an existence to appearance purely vegetative. In their obscure and blind impulse, have they consciousness or instinct? Do they know what takes place at the three-thousandth part of an inch from their microscopic bodies? To the Creator alone does the knowledge of this mystery belong.

It would be foreign to the object of this work to enter into minute division of the innumerable creatures which swarm on the ocean and on its confines. We shall perhaps best consult the convenience of our readers by adopting the following simple arrangement of these animals into

I. Protozoa, including the Spongiadæ, Infusoria, and Foraminifera.

II. Polypifera, including the Hydræ, Sertularia, and Pennatulariæ.

III. Echinodermata, or Sea-urchins and Star-fishes.

Our space will prevent our doing more than presenting to the reader in succession the most characteristic types of each of these groups.

I. THE PROTOZOA.

The Protozoares represent animal life reduced to its most simple expression. They are organized atoms, mere animated and moving points, living sparks. As they are the simplest forms of animal life as regards their structure, so also they are the smallest. Their microscopic dimensions hide them from our view. The discovery of the microscope was a necessary step to our becoming acquainted with these beings, whose existence was ignored by the ancient world, and only revealed in the seventeenth century by the discovery of the microscope. When armed with this marvellous instrument, applied to examine the various liquid mediums—as when Leuwenhoek, for example, applied the magnifying glass to the inspection of stagnant water, with its infusions of macerated vegetable and animal substances—when he scrutinized a drop of water borrowed from the ocean, from rivers, or from lakes, he discovered there a new world—a world which will be unveiled in these pages.

Some modern writers believe that the Protozoa is a mere cellular organism, that being the principle and end of organization, such as we find it in the cellular vegetable. According to this hypothesis, the Protozoares would be the cellulars of the animal kingdom, as the Algæ and Mushrooms are of the vegetable world. This idea is so far wrong, that it has been founded upon the empire of pure theory. "In reality," says Paul Gervais and Van Beneden, "the animals to which we extend it very rarely resemble elementary cellulars." The tissue of which the bodies of the Protozoa are composed is habitually destitute of cellular structure. They are formed of a sort of animated jelly, amorphous and diaphanous, and have received from Dujardin the name of Sarcoda, or soft-fleshed animals.

Infinitely varied in their form, the Protozoares are furnished with vibratile cilia, which are organs of locomotion belonging to the lower animals inhabiting the liquid element. Their bodies are sometimes naked, sometimes covered with a siliceous, chalky, or membranous cuirass. They are divided into two great classes, the Rhizopoda and Infusoria.

Spongia.

The Sponge is a natural production, which has been known from times of the highest antiquity. Aristotle, Pliny, and all other writers who occupied themselves with natural history in ancient times, are agreed in according to it a sensitive life. They recognize the curious fact that the sponge evades the hand which tries to seize it, and clings to the rocks on which it is rooted, as if it would resist the efforts made to detach it. Pliny, Dioscorides, and their commentators, even formed the idea that sponges were capable of feeling, that they adhered to their native rock by special force, and that they shrunk from the hand which tried to seize them. They even distinguished males from females. Erasmus, however, criticising Pliny, concludes that he may pass over all he has written upon the sponge. The sponge, in short, was to the ancients something between a plant and an animal.

Rondelet, the friend of the celebrated Rabelais, whom the merry curate of Meudon designated under the name of Rondibilis, who was himself a physician and naturalist of Montpellier, denied at first the existence of sensibility in sponges. He originated the idea that these productions belonged to the vegetable world—an idea which Tournefort, Gaspard Bauhin, Rey, and even Linnæus, in the first editions of his "Systema Naturæ," supported by the great authority of their names. Afterwards, influenced by the convincing labours of Trembley and some other observers, Linnæus withdrew the sponges from the vegetable world. He satisfied himself, in short, that certain polypiers much resembled sponges in the nature of their parenchyma, and that, on the other hand, the assimilation of sponges with plants was not such as could be maintained. Neuremberg, Peyssonnel, and Trembley maintain the animal nature of sponges, and their views are adopted by Linnæus, Guettard, Donati, Lamouroux, and Ehrenberg on the Continent, and by Ellis, Fleming, and Grant in England. They live at the bottom of the seas in five to twenty-five fathoms of water, among the clefts and crevices of the rocks, always adhering and attaching themselves, not only to inorganic bodies, but even growing on vegetables and animals, spreading, erect, or pendent, according to the body which supports them and their natural habit.