ing as far as the eye could reach, and thronged to the depth of more than a thousand feet with animalcules, have been traversed by navigators in various parts of the world. In the Indian Ocean especially they hang like red, green, brown, or crimson clouds upon the surface of the main. Captain Kingman passed through a shoal of gelatinous creatures extending twenty-three miles in length, breadth unknown, and whitening the sea so completely that it looked like a plain covered with snow. When a tub was filled with the water, little luminous particles were seen dancing to and fro, and the vessel appeared to be alive with tiny worms and insects. In the Northern Seas, the medusæ are so prodigiously developed, and at the same time so densely packed, that, according to Scoresby, it would require 84,000 persons, calculating as if for their lives or perhaps, more stimulating still, as if for their fortunes-and continuing their labors from the Creation up to the present period, to reckon up the quantity contained in two square miles alone. To these, and similar little scavengers, therefore, is probably committed the task of ridding the ocean of much of the decomposing matter which is brushed from the land, and which might otherwise dispose it to putrescence. Other and equally interesting functions have latterly been ascribed to the salts of the sea. Professor Chapman, of Toronto, has ingeniously suggested that their purpose is to regulate the rate of evaporation, and thus keep those two old champions, Moist and Dry, on terms of tolerable amity. Water charged with salt will give off vapor more slowly than water when perfectly pure. Balance two dishes in a pair of scales, fill the one with brine, the other with liquid from the rain-tub, and the latter will beat the former hollow in the rate at which its contents exhale; indeed, in proportion as the saline solution becomes more and more concentrated will the rise of the water in an aëriform shape appear to be retarded. This, in fact, is just what we might expect; for the salt will naturally cling to the fluid with greater tenacity the less it has to lose. Other circumstances, therefore, being the samesuch, for example, as the fervor of the sun's rays, the pressure of the atmosphere, the amount of humidity already in the air -it follows that whenever the quantity of salt in the ocean is relatively diminished by the influx of fresh water in any particular locality, evaporation advances with greater volubility; whereas, if that quantity be augmented, it proceeds at a tardier rate. If this view be correct-and we fancy the propounder has seized upon one of the secrets of the deep-what a splendid automaton the ocean becomes ! Like the governor of a steam-engine, it contracts its own issues of vapor when the sun begins to fall upon its waters with unwarrantable freedom, and increases them when the land has been unduly drained, or the moisture in the atmosphere inordinately precipitated. As the winds whistle over Neptune's domain he seems to say: "I feel that I am growing too saline to-day; you can't, therefore, want much humidity on shore; send me back the surplus either in river or in shower, and when the accounts between sea and land are balanced, you shall receive your usual freight with pleasure. Unless our books are duly squared, and sun and ocean, and wind and stream settle their mutual transactions with punctuality, it would soon be all over with the world." The great business of these saline matters, however, according to Lieutenant Maury, whose ocean studies preeminently entitle him to the appellation of the Philosopher of the Sea, is to keep the abyss of waters in constant motion. To him these humble ingredients are vast dynamic powers. Sea-water is heavier than river in the proportion of 1028 to 1010. A man feels more buoyant whilst swimming off Ramsgate than he does when bathing in the fish-pond at home. Rain-water will float on brackish water; and sailors sometimes take advantage of this fact, as was the case in the expedition of the Adventure and Beagle, where the crews, on one occasion, obtained a potable fluid from the surface of the ocean by inserting the hose of their pumps into the supernatant liquid, whereas, had they gone a few inches deep, they would have drawn up a beverage fit only for naiads and mermen. Now, suppose that evaporation is proceeding rapidly from any tropical tract in the Atlantic or Pacific; of course the consequence will be a lowering of the level, and water must necessarily press in from all sides to fill up the great dimple. Since, however, the vapor which is exhaled is fresh, the fluid left behind must increase in gravity proportionately to the legacy of salt it has just received. What follows? A flow of liquid being determined to the excavat-, this question by referring to those armies ed spot, a current of denser water will of creatures which are employed in exalso be established in a contrary direction. tracting saline materials from the water, For as the fresh water scooped out from some for their shells, some for their skelthe sea in the region of evaporation is etons, some for their habitations. Beds only borrowed for a time, and must de- of marl, banks of shell, and deposits of scend in some other spot, which may be infusoria have been formed in the ancient called the region of precipitation, it will oceans, and the same processes are on foot lessen the specific gravity of the upper in our existing seas. The coralline archistratum of the ocean where it alights, and tects are ever busy in the warmer waters then draining off towards the original of our globe, and huge masses of masonry point of disturbance, the equilibrium must are slowly rising, compared with which be restored by the transfer of the weigh- our human erections are mere card-houses. tier, because saliner, liquid to the compen- To these animals must evidently belong sating parts. Thus, speaking generally, the power of extracting the carbonate of the sea is kept in wholesome excitement lime and other mineral substances they by a wonderful system of circulation, in may require from the transparent wave. which the chloride of sodium and other ingredients figure as important ministering forces. "We have a surface-current of saltish water from the poles towards the equator, and an under-current of water, salter and heavier, from the equator to the poles. This under-current supplies in a great measure the salt which the upper-current, freighted with fresh water from the clouds and rivers, carries back." How beautifully are the equities of the great abyss maintained! Further, it will be seen that in an ocean of salt water a system of vertical circulation must prevail which could not obtain in an ocean of fresh; for, as the surface layer is robbed by evaporation, and its density is consequently augmented, it must sink, whilst the less briny layer beneath will ascend. In the fact, therefore, that a drop of water overdosed with salt will give place to the lighter molecule beneath, we discover another exquisite provision for a perpetual "turn-over" in the liquid mass. But this is not all; the salts not only serve to keep the pulses of the ocean in play, but they are essential to the existence of myriads of living things. Without adverting to the fact that the finny inhabitants of the deep would mostly perish in a fresh-water medium, let us point to the peculiar relationship which subsists between the saline ingredients and one class of marine laborers. Why does not the ocean grow salter every day? Why does it not threaten to become as briny as the Dead Sea and other imprisoned sheets? There must be some means by which the perpetual additions from the shores are neutralized, or at any rate kept in subjection. Maury solves What amount is thus quarried from the waters it would be impossible to surmise; but, considering the number of the workmen, and the magnitude of the piles they have completed, their influence must tell with some power upon the composition of the sea. That it constitutes the sole agency by which the saline additions are held in check can not be admitted, because some of these elements only are required for the purposes of the little operatives. But it is singular to observe how each pigmy mason assists in the great task, which must on no account be neglected, of keeping the waters in ceaseless circulation. Down in the deep the coral insect is at work on the huge edifice which he and his companions have been bidden by instinct to construct. He wants stone: he obtains it from the water around him. How, no one can say: it is one of the mysteries of vital chemistry we are unable to explain. But in extracting the material he requires from any particular drop, that drop necessarily becomes lighter than those above, and therefore ascends to the surface; another, of course, descends to take its place, and suffer a similar loss in turn. Thus, rising and falling like the corves in a pit, the watery atoms are kept in action by the submarine artificers; and though the depth at which they toil is limited, being confined to some thirty fathoms, yet within that range they move the whole mass of fluid overhead, though apparently unmoved and unmoving themselves. And, as if to show that all the powers of nature, whether great or small, play into each other's hands, let it be observed that the sun and winds seem to take thought for the builders of these sunken piles. Do they not, by abstract ing the vapor from the surface, concentrate the saline materials, and send down the drops loaded with mineral, in order that the industrious creatures may pick out what is requisite for their work, and then return them aloft for a further supply? Since, then, motion is the life of the sea, many causes conspire to keep it in a state of sleepless agitation. The most notable of these is the moon. It is surely a striking fact that a puny globe, revolving at the distance of 240,000 miles from our earth, should lift the waters of the ocean and compel huge ripples to course across its surface in regular succession. The Man in the Moon-for to him may we not ascribe this amiable service ?-deserves more thanks from us terrestrials than we can possibly render. To work the tidegauges of the planet, to fill and empty our harbors, to cover our beaches with magnificent rollers, to clear away the abominations of our polluted rivers, to maintain a regular systole and diastole in the oceanheart, are tasks which that renowned individual executes with exemplary patience and precision. Yonder, in the great silent sea which hides the mysteries of the South Pole, the water begins to heave under his sinewy pull. If the sun should be in conjunction or opposition, he too, though with inferior force, joins in the billowy game. A broad wave is formed, which rushes, or seems to rush, to the north, for the particles have no progressive motion, but simply leap upwards, as if in a vain struggle to reach the moon. Following the course of that wave into the Indian Ocean, you would find that, in about twenty-two hours from the time it appeared at the southern extremity of New-Zealand, it was riding in the Delta of the Ganges, and penetrating into the rivers of Hindostan. Meanwhile, another branch of the great billow makes for the African coast, and rolls into the Atlantic after doubling the Cape of Many Storms. In three hours from the time of its entrance into the noble basin, it sweeps in subdued grandeur past the little "volcanic cinder," Napoleon's rocky prison, where it attains a hight of about two or three feet only. In three hours more it crosses the Line, and, after a further voyage of ten, it flows into the mouth of the English Channel, and prepares to wash the feet of the Ruler of the Waves. Most lovingly does that broad undulation twine round the home of Britannia. Whilst one portion enters the Straits of Dover, another glides up the Irish Channel; and a third, sweeping along the western coast of Erin, and curving round the Shetland Islands, actually descends the German Ocean, where it rejoins the advancing tide off the mouth of the Thames, as if to pay double honor to the maritime mistress of the world. And not less lingeringly than lovingly does it perform this part of its journey; for though in some stages of its progress it moves at the rate of a thousand miles an hour, it requires upwards of twenty hours to pass from Cape Clear, at the extremity of Ireland, to the Nore. It need scarcely be said that these giant billows, which follow each other from their nursery in the Antarctic Ocean at intervals of a dozen hours, are affected in their course by the obstructions they encounter. Where the Pacific, for example, is blockaded by great coral ramparts, and spotted by numerous fair islands, He of the moon can find but little scope for his burly pastime; for the tidal wave from the south can not penetrate freely unto that spacious playground. But there are circumstances under which he gambols his strength away in a striking and boisterous manner. In certain estuaries and rivers he produces those magnificent rushes of water called bores or eagres. For the full development of this phenomenon, a gradually narrowing channel and peculiar configuration of ground are required. Some of our British streams, the Severn, the Trent, the Solway Frith, for example, are favorably organized for this purpose. But it is in the Amazon and the rivers of India and China that the tidal wave, now an advancing mass, assumes its most imposing proportions. One of these eagres in the Tsien-Tsang river has been vividly described by Dr. Macgowan in a commnnication to the Royal Asiatic Society: gathered in the streets running at right-angles "As the hour of flood-tide approached, crowds with the Tsien-Tsang, but at safe distances. My position was a terrace in front of the Triwave Temple, which afforded a good view of the entire scene. On a sudden all traffic in the thronged mart was suspended; porters cleared the front street of every description of merchandise; boatmen ceased loading and unloading stream, so that a few moments sufficed to give their vessels, and put out into the middle of the a deserted appearance to the busiest part of one of the busiest cities of Asia. The center of the river teemed with craft, from small boats |