stream at top into two; but it unites again long before it has got to the bottom. The noise of the fall is heard at several leagues distance; and the fury of the waters at the bottom of their fall is inconceivable. The dashing produces a mist that rises to the very clouds; and that produces a most beautiful rainbow, when the sun shines. It may easily be conceived, that such a cataract quite destroys the navigation of the stream; and yet some Indian canoes, as it is said, have been known to venture down it with safety.

Of those rivers that lose themselves in the sands, or are swallowed up by chasms in the earth, we have various information. What we are told by the ancients, of the Alpheus, in Aracadia, that sinks into the ground, and rises again near Syracuse, in Sicily, where it takes the name of Arethusa, is rather more known than credited. But we have better information with respect to the river Tigris being lost in this manner under Mount Taurus; of the Guadalquiver, in Spain, being buried in the sands; of the river Greata, in Yorkshire, running under ground, and rising again; and even of the great Rhine itself, a part of which is no doubt lost in the sands a little above Leydon. But it ought to be observed of this river, that by much the greatest part arrives at the ocean; for, although the ancient channel which fell into the sea, a little to the west of that city, is now entirely choked up, yet there are still a number of small canals, that carry a great body of waters to the sea; and, besides, it has also two very large openings, the Lech and the Waal, below Rotterdam, by which it empties itself abundantly.

Be this as it will, nothing is more common in sultry and sandy deserts, than rivers being thus either lost in the sands, or entirely dried up by the sun. And hence we see, that under the line the small rivers are but few; for such little streams as are common in Europe, and which with us receive the name of rivers, would quickly evaporate, in those parching and extensive deserts. It is even confidently asserted, that the great river Niger is thus lost before it reaches the ocean; and that its supposed mouths, the Gambia and the Senegal, are distinct rivers, that come a vast way from the interior parts of the country. It appears, therefore, that the rivers under the line are large; but it is otherwise at the poles, where they must necessarily be small. In that desolate reigon, as the inountains are covered with perpetual ice, which melts but little, or not at all, the springs and rivulets are furnished with a very small supply. Here, therefore, men and beasts would perish, and die for thirst, if Providence had not ordered that in the hardest winter thaws should intervene, which deposit a small quantity of snow-water in pools under the ice; and from this source the wretched inhabitants drain a scanty beverage.

Thus, whatever quarter of the globe we turn to, we shall find new reasons to be satisfied with that part of it in which we reside. Our rivers furnish all the plenty of the African stream, without its inundation; they have all the coolness of the polar rivulet, with a more constant supply; they may want the terrible magnificence of huge cataracts or extensive lakes, but they are more navigable and more transparent; though less deep and rapid than the rivers of the torrid zone, they are more manageable, and only wait the will of man to take their direction. The rivers of the torrid zone, like the monarchs of the country, rule with despotic tyrannyprofuse in their bounties, and ungovernable in their rage. The rivers of Europe, like its kings, are the friends, and not the oppressors, of its people-bounded by no limits, abridged in the power of doing ill, directed by human sagacity, and only at freedom to distribute happiness and plenty.

CHAP. XV.

OF THE OCEAN IN GENERAL, AND OF ITS SOFTNESS.

If we look upon a map of the world, we shall find that the ocean occupies considerably more of the globe than the land is found to do. This immense body of waters is diffused round both the old and new continent to the south, and may surround them also to the north for what we know; but the ice in those regions has stopped our inquiries. Although the ocean, properly speaking, is but one extensive sheet of waters continued over every part of the globe without interruption, and although no part of it is divided from the rest, yet geographers have distinguished it by different names, as the Atlantic or Western Ocean, the Northern Ocean, the Southern Ocean, the Pacific Ocean, and the Indian Ocean. Others have divided it differently, and given other names, as the Frozen Ocean, the Inferior Ocean, or the American Ocean. But all these being arbitrary distinctions, and not of Nature's making, the naturalist may consider them with indifference.

In this vast receptacle almost all the rivers of the earth ultimately terminate; nor do such great supplies seem to increase its stores, for it is neither apparently swollen by their tribute, nor diminished by their failure; it still continues the same. Indeed, what is the quantity of water of all the rivers and lakes in the world, compared to that contained in this great receptacle? If we should offer to make a rude estimate, we shall find that all the rivers in the world, flowing into the bed of the sea, with a continuance of their present stores, would take up at least eight hundred years to fill it to its present height. For, supposing the sea to be eighty-five millions of square miles in extent, and a quarter of a mile, upon an average, in depth, this, upon calculation, will give above twenty-one millions of cubic miles of water as the contents of the whole ocean. Now, to estimate the quantity of water which all the rivers supply, take one of them; the Po, for instance, the quantity of whose discharge into the sea, is known to be one cubic mile of water in twenty-six days. Now it will be found, upon a rude computation, from the quantity of ground the Po, with its influent streams, covers, that all the rivers of the world furnish about two thousand times that quantity of water. In the space of a year, therefore, they will have discharged into the sea about twenty-six thousand cubic miles of water; and not till eight hundred years will they have discharged as much water as it contained in the sea at present. I have not troubled the reader with the odd numbers, lest he should imagine I was giving precision to a subject that is incapable of it.

Thus great is the assemblage of waters diffused round our habitable globe; and yet, immeasurable as they seem, they are mostly rendered subservient to the necessities and the conveniences of so little a being as man. Nevertheless, if it shouid be asked whether they be made for him alone, the question is not easily resolved. Some philosophers have perceived so much analogy to man in the formation of the ocean, that they have not hesitated to assert its being made for him alone. The distribution of land and water, say they, is admirable; the one being laid against the other so skil fully, that there is a just equipoise of the whole globe Thus the Northern Ocean balances against the Southern; and the new continent is an exact counterweight to the old. As to any objection from the ocean's occupying too large a share of the globe, they contend that there could not have been a smaller surface employed to supply the earth with a due share of evaporation. On the other hand, some take the gloomy side of the question: they either magnify its apparent defects, or assert that what seems defects to us may be real beauties to some wiser order of beings. They observe that multitudes

of animals are concealed in the ocean, and but a small part of them are known; the rest, therefore, they fail not to say, were certainly made for their own benefit, and not for ours. How far either of these opinions be just I will not presume to determine; but of this we are certain, that God has endowed us with abilities to turn this great extent of waters to our own advantage. He has made these things, perhaps, for other uses; but He has given us faculties to convert them to our own. This much agitated question, therefore, seems to terminate here. We shall never know whether the things of this world have been made for our use; but we very well know that we have been made to enjoy them. Let us, then, boldly affirm that the earth and all its wonders are ours, since we are furnished with powers to force them into our service. Man is the lord of all the sublunary creation; the howling savage, the winding serpent, with all the untameable and rebellious offspring of Nature, are destroyed in the contest, or driven at a distance from his habitations. The extensive and tempestuous ocean, instead of limiting or equalising his power, only serves to assist his industry and enlarge the sphere of his enjoyments. Its billows and its monsters, instead of presenting a scene of terror, only call up the courage of this intrepid little being; and the great est dangers that man now fears on the deep is from his fellow-creatures. Indeed, when I consider the human race as Nature has formed them, there is but little of the habitable globe that seems made for them; but when I consider them as accumulating the experience of ages in commanding the earth, there is nothing so great or so terrible. What a poor contemptible being is the naked savage, standing on the beach of the ocean, and trembling at its tumults! How little capable is he of converting its terrors into benefits, or of saying-Behold an element made wholly for my enjoyment! He considers it as an angry deity, and pays it the homage of submission. But it is far different when he has exercised his mental powers-when he has learned to find his own superiority, and to make it subservient to his command. It is then that his dignity begins to appear, and that the true Deity is justly praised for having been mindful of man-for having given him the earth for his habitation and the sea for an inheritance.

This power which man has obtained over the ocean was at first enjoyed in common; and none pretended to a right in that element where all seemed intruders. The sea, therefore, was open to all till the time of the Emperor Justinian. His successor, Leo, granted such as were in possession of the shore the sole right of fishing before their respective territories. The Thracian Bosphorus was the first that was thus appropriated; and from that time it has been the struggle of most of the powers of Europe to obtain an exclusive right in this element. The republic of Venice claims the Adriatic; the Danes are in possession of the Baltic; but the English have a more extensive claim to the empire of all the seas encompassing England, Scotland, and Ireland; and although these have been long contested, yet they are now considered as their indisputable property. Every one knows that the great power of the nation is exerted on this element, and that the instant England ceases to be superior upon the ocean its safety begins to be precarious.

It is in some measure owing to our dependence upon the sea, and to our commerce there, that we are so well acquainted with its extent and figure. The bays, gulfs, currents, and shallows of the ocean are much better known and examined than the provinces and kingdoms of the earth itself. The hopes of acquiring wealth by commerce has carried man to much greater lengths than the desire of gaining information could have done. In consequence of this, there is scarce a strait or a harbour, scarce a rock or a quicksand, scarce an inflexion of the shore or the jutting of a promontory,

that has not been minutely described. But as these present very little entertainment to the imagination, or delight to any but those whose pursuits are lucrative, they need not be dwelt upon here. While the merchant and the mariner are solicitous in describing currents and soundings, the naturalist is employed in observing wonders, though not so beneficial, yet to him of a much more important nature. The saltness of the sea seems to be the foremost

Whence the sea has derived that peculiar bitterish saltness which we find in it, appears by Aristotle to have exercised the curiosity of naturalists in all ages. He supposed (and mankind were for ages content with the solution) that the sun continually raised dry saline exhalations from the earth, and deposited them upon the sea; and hence, say his followers, the waters of the sea are more salt at top than at bottom. But, unfortunately for this opinion, neither of the facts is true. Sea-salt is not to be raised by the vapours of the sun; and seawater is not salter at the top than at the bottom. Mr. Bohours is of opinion that the Creator gave the waters of the ocean their saltness at the beginning, not only to prevent their corruption, but to enable them to bear greater burthens. But their saltness does not prevent their corruption; for stagnant sea-water, like fresh, soon grows putrid; and, as for their bearing greater burthens, fresh water answers all the purposes of navigation quite as well. The established opinion, therefore, is that o Boyle, who supposes, That the sea's saltness is supplied not only from rocks or masses of salt at the bottom of the sea, but also from the salt which the rains and rivers and other waters dissolve in their passage through many parts of the earth, and at length carry with them to the sea." But as there is a difference in the taste of rock-salt found on land and that dissolved in the waters of the ocean, this may be produced by the plenty of nitrous and bitumenous bodies that, with the salts, are washed into that great receptacle. These substances, being thus once carried to the sea, must for ever remain there; for they do not rise by evaporation so as to be returned back from whence they came. Nothing but the fresh waters of the sea rise in vapours, and all the saltness remains behind. From hence it follows that every year the sea must be come more and more salt; and this speculation Dr. Halley carries so far, as to lay down a method of finding out the age of the world by the saltness of its waters. "For if it be observed," says he, "what quantity of salt is at present contained in a certain weight of water, taken up from the Caspian Sea, for example, and, after some centuries, what greater quantity of salt is contained in the same weight of water taken from the same place, we may conclude that, in proportion as the saltness has increased in a certain time, so much must it have increased before that time; and we may thus, by the rule of proportion, make an estimate of the whole time wherein the water would acquire the degree of saltness it should then be possessed of." All this may be fine; however, an experiment, begun in this century which is not to be completed till some centuries hence, is rather a little mortifying to modern curiosity; and I am induced to think the inhabitants round the Caspian Sea will not be apt to undertake the inquiry.

This saltness is found to prevail in every part of the ocean; and as much at the surface as at the bottom. It is also found in all those seas that communicate with, the ocean; rather in a less degree.

The great lakes, likewise, that have no outlets nor com. munication with the ocean, are found to be salt; but some of them in less proportion. On the contrary, all. those lakes through which the rivers run into the sea, however extensive they be, are, notwithstanding, very fresh: for the rivers do not deposit their salts in the bed of the lake, but carry them with their currents into the ocean. Thus the lakes Ontario and Erie, in North America, although for magnitude they may be considered

as inland seas, are, nevertheless, fresh-water lakes; and kept so by the river St. Lawrence, which passes through them. But those lakes that have no communication with the sea, nor any rivers going out, although they be less than the former, are, however, always salt. Thus, that which goes by the name of the Dead Sea, though very small when compared to those already mentioned, is so exceedingly salt, that its waters seem scarce capable of dissolving any more. The lakes of Mexico and Titicaca, in Peru. though of no great extent, are, notwithstanding, salt-and both for the same reason.

Those who are willing to turn all things to the best, have not failed to consider this saltness of the sea as a peculiar blessing from Providence, in order to keep so great an element sweet and wholesome. What foundation there may be in the remark I will not pretend to determine; but we shall shortly find a much better cause for its being kept sweet, namely, its motion.

On the other hand, there have been many who have considered the subject in a different light, and have tried every endeavour to make salt-water fresh, so as to supply the wants of mariners in long voyages, or when exhausted of their ordinary stores. At first it was supposed simple distillation would do; but it was soon found that the bitter part of the water still kept mixed. It was then tried by uniting salt of tartar with sea-water, and distilling both; but here the expense was greater than the advantage- Calcined bones were next thought of; but a hogshead of calcined bones, carried to sea, would take up as much room as a hogshead of water, and was more hard to be obtained. In this state, therefore, have the attempts to sweeten sea-water rested; the chymist satisfied with the reality of his invention; and the mariner convinced of its being useless. I cannot, therefore, avoid mentioning a kind of succedaneum which has been lately conceived to answer the purposes of fresh-water, when mariners are quite exhausted. It is well known that persons who go into a warm bath come out several ounces heavier than they went in; their bodies having imbibed a correspondent quantity of water. This more particularly happens if they have been previously debarred from drinking, or go in with a violent thirst; which they quickly find quenched and their spirits restored. It was supposed, that in case of a total failure of fresh-water at sea, a warm bath might be made of sea-water for the use of mariners; and that their pores would thus imbibe the fluid without any of its salts, which would be seen to crystalize on the surface of their bodies. In this manner, it is supposed, a sufficient quantity of moisture may be procured to sustain life, till time or accident furnish a more copious supply.

But, however this may be, the saltness of the sea can by no means be considered as a principal cause in preserving its waters from putrefaction. The ocean has its currents, like rivers, which circulate its contents round the globe; and these may be said to be the great agents that keep it sweet and wholesome. Its saltness alone would by no means answer this purpose: and some have even imagined, that the various substances with which it is mixed rather tend to promote putrescence than impede it. Sir Robert Hawkins, one of our most enenlightened navigators, gives the following account of a . calm, in which the sea, continuing for some time without motion, began to assume a very formidable appearance. "Were it not," says he "for the moving of the sea, by the force of winds, tides, and currents, it would corrupt all the world. The experiment of this I saw in the year 1590, lying with a fleet about the islands of Azores, almost six months; the greatest part of which time we were becalmed. Upon which all the sea became so replenished with several sorts of jellies, and forms of serpents, adders, and snakes, as seemed wonderful: some green, some black, some yellow, some white, some of divers colours; and many of them had life; and some tliere were a yard and a half and two yards long; which,

had I not seen, I could hardly have believed, and hereof are witnesses all the company of the ships which were then present; so that hardly a man could draw a bucket of water clear of some corruption. In which voyage, towards the end thereof, many of every ship fell sick, and began to die apace. But the speedy passage into our country was a remedy to the crazed, and preservative for those that were not touched."

This shows, abundantly, how little the sea's saltress was capable of preserving it from putrefaction: but to put the matter beyond all doubt, Mr. Boyle kept a quantity of sea-water, taken up in the English Channel, for some time barrelled up, and in the space of a few weeks it began to acquire a foetid smell. He was also assured by one of his acquaintance, who was becalmed for twelve or fourteen days in the Indian Sea, that the water for want of motion began to stink; and that, had it continued much longer, the stench would probably have poisoned him. It is the motion, therefore, and not the saltness of the sea, that preserves it in its present state of salubrity-and this, most probably, by dashing and breaking in pieces the rudiments, if I may so call them, of the various animals that would otherwise breed there and putrefy.

There are some advantages, however, derived from the saltness of the sea. Its waters, being evaporated, furnish that salt which is used for domestic purposes; and although in some places it is made from springs, and in others dug out of mines, yet the greatest quantity is made only from the sea. That which is called "baysalt" (from its coming to us from the Bay of Biscay) is a stronger kind, made from the sun; that called common-salt" is evaporated in pans over the fire, and is of a much inferior quality to the former.

Another benefit arising from the quantity of salt dissolved in the sea is, that it thus becomes heavier, and consequently more buoyant. Mr. Boyle, who examined the difference between sea-water and fresh, found that the former appeared to be about a forty-fifth part heavier than the latter. Those, also, who have had opportunities of bathing in the sea pretend to have experienced a much greater ease in swimming than in fresh water. However, as we see they have only a forty-fifth part more of their weight sustained by it, I am apt to doubt whether so minute a difference can be practically perceivable. Be this as it may, as sea-water alters in its weight from fresh, so it is found also to differ from itself in different parts of the ocean. In general it is perceived to be heavier, and consequently salter, the nearer we approach the line.

But there is an advantage arising from the saltness of the waters of the sea much greater than what has yet been mentioned-which is, that their congelation is thus retarded. Some, indeed, have gone so far as to say that sea-water never freezes; but this is an assertion contra dicted by experience. However, it is certain that it requires a much greater degree of cold to freeze it than fresh water; so that, while rivers and springs are seen converted into one solid body of ice, the sea is always fit for navigation, and no way affected by the coldness of the severest winter. It is therefore one of the greatest blessings we derive from this element, that, when on land all the stores of Nature are locked up from us, we find the sea ever open to our necessities, and patient of the hand of industry.

But it must not be supposed that because in our temperate climate we never see the sea frozen it is in the same manner open in every part of it; a very little acquaintance with the accounts of mariners must have informed us, that at the polar regions it is embarrassed with mountains and moving sheets of ice that often render it impassable. These tremendous floats are of different magnitudes-sometimes rising more than a thousand feet above the surface of the water, sometimes diffused into plains of above two hundred leagues in

length, and in many parts sixty or eighty broad. They are usually divided by fissures, one piece following another so close that a person may step from one to the other. Sometimes mountains are seen rising amidst these plains, and presenting the appearance of a variegated landscape, with hills and valleys, houses, churches, and towers. These are appearances in which all naturalists are agreed; but the great contest is respecting their formation. Mr. Buffon asserts that they are formed from fresh water alone, which, congealing at the mouths of great rivers, accumulate those huge masses that disturb navigation. However, this great naturalist seems not to have been aware that there are two sorts of ice floating in these seas-the flat ice and the mountain ice; the one formed of sea-water only-the other of fresh. The flat or driving ice is entirely composed of seawater, which upon dissolution is found to be salt, and is readily distinguished from the mountain or fresh-water ice by its whiteness and want of transparency. This ice is much more terrible to mariners than that which rises up in lumps: a ship can avoid the one, as it is seen at a distance; but often gets in among the other, which, sometimes closing, crushes it to pieces. This, which manifestly has a different origin from the fresh-water ice, may perhaps have been produced from the Icy Sea, heneath the pole; or along the coasts of Spitzbergen or Nova Zembla.

The mountain ice, as was said, is different in every respect, being formed of fresh water, and appearing hard and transparent; it is generally of a pale-green colour, though some are of a beautiful sky blue; many large masses also appear grey, and some black. If examined more closely, they are found to be incorporated with earth, stones, and brushwood washed from the shore. On these, also, are sometimes found not only earth, but nests with birds' eggs, at several hundred miles from land. The generality of these, though almost totally fresh, have a thick crust of salt water frozen upon them, probably from the power that ice has sometimes to produce ice. Such mountains as are here described are most usually found at spring-time, and after a violent storm, driving out to sea, where they at first terrify the mariner, and are soon after dashed to pieces by the continual washing of the waves, or driven into the warmer regions of the south, there to be melted away. They sometimes, however, strike back upon their native shores, where they seem to take root at the feet of the mountains, and (as Martius tells us) are sometimes higher than the mountains themselves. Those seen by him were blue, full of clefts and cavities made by the rain, and crowned with snow, which, alternately thawing and freezing every year, augmented their size. These, composed of materials more solid than that driving at sea, presented a variety of agreeable figures to the eye that, with a little help from fancy, assumed the appearance of trees in blossom; the inside of churches, with arches, pillars, and windows, and the blue-coloured rays darting from within, presented the resemblance of a gloria.

If we inquire into the origin and formation of these which, as we see, are very different from the former-I think we have a very satisfactory account in the following passage from Crantz:-" These mountains of ice," he says, are not salt, like sea water, but sweet; and therefore can be formed nowhere except on the mountains, in rivers, in caverns, and against the hills near the sea-shore. The mountains of Greenland are so high, that the snow which falls upon them, particularly on the north side, is in one night's time wholly converted into ice. They also contain clefts and cavities where the sun seldom or never injects his rays. Besides these are projections, or landing-places, on the declivities of the steepest hills, where the rain and snow-water lodge and quickly congeal. When the accumulated flakes of snow slide down, or fall with the rain from the eminences above on these prominences; or, when here and

there a mountain spring comes rolling down to such a lodging-place where the ice has already seated itself, they all freeze, and add their tribute to it. This, by degrees, waxes to a body of ice that can no more be overpowered by the sun, and which, though it may at certain seasons diminish by a thaw, yet upon the whole, through annual acquisitions, it assumes an annual growth. Such a body of ice is often prominent far over the rocks. It does not melt on the upper surface, but underneath, and often cracks into many larger or smaller clefts, from whence the thawed water trickles out. By this it becomes at last so weak, that, being overloaded with its own ponderous bulk, it breaks loose, and tumbles down the rocks with a terrible crash. Where it happens to overhang a precipice on the shore, it plunges into the deep with a shock like thunder, and with such an agitation of the water as will overturn a boat at some distance, as many a poor Greenlander has fatally experienced." Thus are these amazing ice-mountains launched forth to sea, and found floating in the waters round both the poles. It is these that have hindered mariners from discovering the extensive countries which lie round the South Pole, and which probably block up the passage to China by the north. I will conclude this chapter with one effect more produced by the saltness of the sea, which is the luminous appearance of its waves in the night. All who have been spectators of a sea by night a little ruffled by winds, seldom fail of observing its fiery brightness. In some places it shines as far as the eye can reach; at other times, only when the waves boom against the side of the vessel, or the oar dashes into the water. Some seas shine often-others more seldom; some, ever when particular winds blow-others within a narrow compass; a long tract of land being seen along the surface, whilst all the rest is hid in total darkness. It is not easy to account for these extraordinary appearances; some have supposed that a number of luminous insects produced the effect-and this is really sometimes the case; in general, however, they have every resemblance to that light produced by electricity, and probably arise from the agitation and dashing of the saline particles of the fluid against each other. But the manner in which this is done for we can produce nothing similar by any experiments hitherto made-remains for some happier accident to discover. Our progress in the knowledge of Nature is slow; and it is a mortifying consideration, that we are, hitherto, more indebted for success to chance than industry.

CHAP. XVI.

OF THE TIDES, MOTION, AND CURRENTS OF THE SEA, WITH THEIR EFFECTS.

It was said in the former chapter that the waters of the sea were kept sweet by their motion, without which they would soon putrefy and spread universal infection. If we look for final causes, here indeed we have a great and an obvions one that presents itself before us. Had the sea been made without motion, and resembling a pool of stagnant water, the nobler races of Animated Nature would shortly be at an end. Nothing would then be left alive but swarms of ill-formed creatures, with scarce more than vegetable life, and subsisting by putrefaction. Were this extensive bed of waters entirely quiescent, millions of the smaller reptile kinds would there find a proper retreat to breed and multiply in; they would find there no agitation-no concussion in the parts of the fluid to crush their feeble frames, or to force them from the places where they were bred; there they would multiply in security and ease, enjoy a short life, and putrefying, thus again give nourishment to