duces the same effect as gunpowder-splitting the most solid rocks, and thus shattering the summits of the mountain. But not rocks alone, but whole mountains, are by various causes, disunited from each other. We see in many parts of the Alps amazing clefts, the sides of which so exactly correspond with the opposite, that no doubt can be made of there having been once joined together. At Cajeta, in Italy, a mountain was split in this manner by the earthquake; and there is a passage opened through it that appears as if elaborately done by the industry of man. In the Andes these breaches are frequently seen. That at Thermopyle, in Greece, has been long famous. The mountain of the Troglodytes, in Arabia, has thus a passage through it; and that in Savoy-which Nature began, and which Victor Amadeus completed-is an instance of the same kind. We have accounts of some of these disruptions immediately after their happening. In the month of June, in the year 1714, a part of the mountain of Diableret, in the district of Valais, in France, suddenly fell down between two and three o'clock in the afternoon, the weather being very calm and serene. It was of a conical figure, and destroyed fifty-five cottages in the fall. Fifteen persons, together with about a hundred beasts, were also crushed beneath its ruins, which covered an extent of a good league square. The dust it occasioned instantly covered all the neighbourhood in darkness. The heaps of rubbish were more than three hundred feet high. They stopped the current of a river that ran along the plain, which now is formed into several new and deep lakes. There appeared through the whole of this rubbish none of those substances that seemed to indicate that this disruption had been made by means of subterraneous fires. Most probably the base of this rocky mountain was rotted and decayed, and fell without any extraneous violence. In the same manner, in the year 1618, the town of Pleurs, in France, was buried beneath a rocky mountain, at the foot of which it was situated. These accidents and many more that might be enumerated of the same kind-have been produced by various causes; by earthquakes, as in the mountain at Cajeta; or by being decayed at the bottom, as at Diableret. But the most general way is by the foundation of one part of the mountain being hollowed by waters, and thus, wanting a support, breaking from the other. Thus, it generally has been found in the great chasms of the Alps; and thus it almost always is known in those disruptions of hills which are known by the name of land-slips. These are nothing more than the sliding down of a higher piece of ground, disrooted from its situation by subterraneous inundations, and settling itself upon the plain below. There is not an appearance in all Nature that so much astonished our ancestors as these land-slips. In fact, to behold a large upland, with its houses, its corn, and its cattle, at once loosened from its place, and floating, as it were, upon the subjacent water-to behold it quitting its ancient situation, and travelling forward like a ship in quest of adventures, this is certainly one of the most extraordinary appearances that can be imagined, and, to a people ignorant of the powers of Nature, might well be considered as a prodigy. Accordingly, we find all our old historians mentioning it as an omen of approaching calamities. In this more enlightened age, however, its cause is very well known; and, instead of exciting ominous apprehensions in the populace, it only gives rise to some very ridiculous law-suits among them about whose the property shall be-whether the land which has thus slipt shall belong to the original possesser, or to him upon whose grounds it has encroached and settled. What has been the determination of the judges is not so well known, but the circumstances of the slips have been minutely and exactly described In the lands of Slatberg, in the kingdom of Iceland, there stood a declivity gradually ascending for nearly half a mile. In the year 1713, on the 10th of March, the inhabitants perceived a crack on its side, somewhat like a furrow made with a plough, which they imputed to the effects of lightning, as there had been thunder the night before. However, on the evening of the same day, they were surprised to hear a hideous, confused noise, issuing all round from the side of the hill; and their curiosity being raised they searched the place. There, to their amazement, they found the earth for nearly five acres all in gentle motion, and sliding down the hill upon the subjacent plain. This motion continued the remaining part of the day and the whole night; nor did the noise cease during the whole time-proceeding, probably, from the attrition of the ground beneath. The day following, however, this strange journey down the hill ceased entirely, and above an acre of the meadow below was found covered with what before composed a part of the declivity. However, these slips, when a whole mountain's side seems to descend, happen but very rarely. There are some of another kind, however, much more common, and, as they are always sudden, much more dangerous. These are show-slips-well known and greatly dreaded by travellers. It often happens, that when snow has long been accumulated on the tops and on the sides of mountains, it is borne down the precipice either by means of tempests or its own melting. At first, when loosened, the volume in motion is but small; but it gathers as it continues to roll, and, by the time it has reached the habitable parts of the mountain, is generally grown of enormous bulk. Wherever it rolls it levels all things in its way, or buries them in unavoidable destruction. Instead of rolling, it sometimes is found to slide along from the top; yet even thus it is generally as fatal as before. Nevertheless, we have had an instance, a few years ago, of a small family in Germany that lived for above a fortnight beneath one of these snow-slips. Although they were buried during the whole time, in utter darkness and under a bed of some hundred feet deep, yet they were luckily taken out alive-the weight of the snow being supported by a beam that kept up the roof, and nourishment being supplied them by the milk of an ass (if I remember right) that was buried under the same ruin But it is not the parts alone that are thus found to subside; whole mountains have been known totally to disappear. Pliny tells us, that in his own time the lofty mountain of Cybotus, together with the city of Eurites, were swallowed by an earthquake. The same fate, he says, attended Phlegium, one of the highest mountains in Ethiopia; which, after one night's concussion, was never seen more. In more modern times, a very noted mountain in the Molucca Islands, known by the name of the "Peak," and remarkable for being seen at a very great distance from sea, was swallowed by an earthquake, and nothing but a lake was left in the place where it stood. Thus, while storms and tempests are levelled against mountains above, earthquakes and waters are undermining them below. All our histories talk of their destruction; and very few new ones (if we except Mount Cenere, and one or two such heaps of cinders) are produced. If mountains, therefore, were of such great utility as some philosophers make them to mankind, it would be a very melancholy consideration that such benefits were diminishing every day. But the truth is, the valleys are fertilised by that earth which is washed from their sides, and the plains become richer in proportion as the mountains decay. D CHAP. XIII. OF WATER. In contemplating Nature, we shall often find the same substances possessed of contrary qualities, and producing opposite effects. Air, which liquifies our substance, dries up another. That fire which is seen to burn up the desert is often found, in other places, to assist the luxuriance of vegetation; and water-which, next to fire, is the most fluid substance upon earth-gives all other bodies their firmness and durability: so that every element seems to be a powerful servant, capable either of good or ill, and only requiring external direction to become the friend or the enemy of mankind. These opposite qualities, in this substance in particular, have not failed to excite the admiration and inquiry of the curious. most fluid body, when mixed with others, gives them consistence and form. Water, by being mixed with earth and ashes and formed into a vessel, when baked before the fire becomes a copel, remarkable for this-that it will bear the utmost force of the hottest furnace that art can contrive. So the Chinese earth, of which porcelain is made, is nothing more than an artificial composition of earth and water united by heat, and which a greater quantity of heat could easily separate. Thus we see a body, extremely fluid of itself, in some measure assuming a new nature by being united with others; we see a body, whose fluid and dissolving qualities are so obvious, giving confidence and hardness to all the substances of the earth. From considerations of this kind, Thales and many of the ancient philosophers held that all things were made of water. In order to confirm this opinion, Helmont made an experiment, by divesting a quantity of That water is the most fluid penetrating body (next to earth of all its oils and salts, and then putting this fire), and the most difficult to confine, is incontestibly earth, so prepared, into an earthen pot which nothing proved by a variety of experiments. A vessel through but rain-water could enter, and planting a willow therein. which water cannot pass may be said to retain anything. The willow grew up to a considerable height and bulk, It may be objected, indeed, that syrups, oils, and honey merely from the accidental aspersion of rain-water; leak through some vessels that water cannot pass while the earth in which it was planted received no through; but this is far from being the result of the sensible diminution. From this experiment he congreater tenuity and fineness of their parts; it is owing eluded that water was the only nourishment of the vegeto the rosin wherewith the wood of such vessels abounds, table tribe; and that, vegetables being the nourishment which oils and syrups have the power of dissolving-so of animals, all organised substances therefore owed their that these fluids, instead of finding their way, may more support and being only to water. But Woodward says properly be said to eat their way through the vessels this is all a mistake; and he endeavours to show that which contain them. However, water will at length water, being impregnated with earthy particles, is only find its way even through these for it is known to the conveyer of such substances into the pores of vege escape through vessels of every substance, glass only tables, rather than increaser of them, by its own bulk. excepted. Other bodies may be found to make their He also shows that water is ever found to afford so much way out more readily indeed—as air, when it finds a less nourishment in proportion as it is putrefied by disvent, will escape at once; and quicksilver, because of its tillation. A plant in distilled water will not grow so weight, quickly penetrates through whatever chinky fast as in water not distilled; and if the same be distilled vessel confines it; but water, though it operates more three or four times over, the plant will scarcely grow at slowly, always finds a more certain issue. As, for in all, or receive any nourishment from it-so that water, stance, it is well known that air will not pass through as such, does not seem the proper nourishment of vege leather, which water will very readily penetrate. Air, tables, but only the vehicle thereof which contains the also, may be retained in a bladder; but water will soon nutritious particles, and carries them through all parts ooze through. And those who drive this to the greatest of the plant. Water, in its pure state, may suffice to degree of precision pretend to say that it will pass extend or swell the parts of a plant, but affords vegetable through pores ten times smaller than air can do. Be matter in a moderate proportion. this as it may, we are very certain that its parts are so small, that they have been actually driven through the pores of gold. This has been proved by the famous Florentine experiment, in which a quantity of water was shut up in a hollow ball of gold, and then pressed with immense force by screws, during which the fluid was seen to ooze out through the pores of the metal, and to stand like a dew upon its surface. As water is thus penetrating and its parts thus minute, it may easily be supposed that they enter into the composition of all bodies-vegetable, animal, and fossil, This every chymist's experience convinces him of; and the mixture is the more obvious, as it can always be separated by a gentle heat from those substances with which it had been united. Fire, as was said, will penetrate where water cannot pass; but then it is not so easily separated. But there is scarce any substance from which water cannot be divorced. The parings or filings of lead, tin, and antimony, by distillation, yield water plentifully; the hardest stones, sea-salt, nitre, vitriol, and sulphur, are found to consist chiefly of water, into which they resolve by force of fire. "AÏl birds, beasts, and fishes," says Newton, "insects, trees, and vegetables, with their parts, grow from water, and by putrefaction return to water again." In short, alnost every substance that we see owes its texture and firmness to the parts of water that mix with its earth; and, deprived of this fluid, it becomes a mass of shapeless dust and ashes. From hence we see, as was above hinted, that this However this be, it is agreed on all sides that water, such as we find it, is far from being a pure simple substance. The most genuine we know is mixed with exhalations and dissolutions of various kinds; and no expedient that has been hitherto discovered is capable of purifying it entirely. If we filter and distil it a thousand times, according to Boerhaave, it will still depose a sediment; and by repeating the process we may evaporate it entirely away, but can never totally remove its impurities. Some, however, assert that water, properly distilled, will have no sediment; and that the little white speck which is found at the bottom of the still is a substance that enters from without. Kircher used to show in his museum a phial of water that had been kept for fifty years hermetically sealed, during which time it had deposed no sediment, but continued as transparent as when first it was put in. How far, therefore, it may be brought to a state of purity by distillation is unknown; but we very well know that all such water as we everywhere see is a bed in which plants, minerals, and animals are found confusedly floating together. Rain-water, which is a fluid of Nature's own distilling, and which has been raised so high by evaporation, is, nevertheless, a very mixed and impure substance. Exhalations of all kinds, whether salts, sulphurs, or metals, make a part of its substance, and tend to increase its weight. If we gather the water that falls after a thunder-clap in a sultry summer's day, and let it settle, we shall find a real salt sticking at the bottom. In winter, however, its impure mixtures are fewer; but still they may be separated by distillation. But as to that which is generally caught pouring from the tops of houses, it is particularly foul, being impregnated with the smoke of the chimneys, the vapour of the slates or tiles, and with other impurities that birds and animals may have deposited there. Besides, though it should be supposed free from all these, it is mixed with a quantity of air, which, after being kept for some time, will be seen to separate. Spring-water is next, in point of purity. This, ac. cording to Dr. Halley, is collected from the air itself; which, being sated with water, and coming to be condensed by the evening's cold, is driven against the tops of the mountains, where, being condensed and collected it trickles down by the sides into the cavities of the earth, and, running for a while under-ground, bubbles in fountains upon the plain. This, having made but a short circulation, has generally had no long time to dissolve or imbibe any sovereign substances by the way. River-water is generally more foul than the former; wherever the stream flows it receives a tincture from its channel. Plants, minerals, and animals, all contribute to add to its impurities: so that such as live at the mouths of great rivers generally are subject to all those disorders which contaminated and unwholesome waters are known to produce. Of all the river-water in the world, that of the Indus and the Thames is said to be the most light and wholesome. The most impure fresh-water that we know is that of stagnated pools and lakes, which, in summer, may be more properly considered as a jelly of floating insects than a collection of water. In this, millions of little reptiles, undisturbed by any current, which might crush their frames to pieces, breed and engender. The whole teems with shapeless life, and only grows more fruitful by increasing putrefaction. Of the purity of all these waters, the lightness and not the transparency ought to be the test. Water may be extremely clean and beautiful to the eye, and yet very much impregnated with mineral particles. In fact, sea-water is the most transparent of any, and yet is well known to contain a large mixture of salt and bitumen. On the contrary, those waters which are lightest have the fewest dissolutions floating in them; and may, therefore, be the most useful for all the purposes of life. But, after all, though much has been said upon this subject, and although waters have been weighed with great assiduity to determine their degree of salubrity, yet neither this, nor their curdling with soap, nor any other philosophical standard whatsoever, will answer the purposes of true information. Experience alone ought to determine the useful or noxious qualities of every spring; and experience assures us, that different kinds of water are adapted to different constitutions. An incontestible proof of this are the many medicinal springs throughout the world, whose pecular benefits are known to the natives of their respective countries. These are of various kinds, according to the different minerals with which they are imprégnated-hot, saline, sulphureous, bitumenous, and oily. But the account of these will come most properly under that of the several minerals by which they are produced. After all, therefore, we must be contented with but an impure mixture for our daily beverage. And yet, perhaps, this very mixture may often be more serviceable to our health than that of a purer kind. We know that it is so with regard to vegetables; and why not, also, in general to man? Be this as it will, if we are desirous of having water in its greatest purity, we are ordered by the curious in this particular to distil it from snow, gathered upon the tops of the highest mountains, and to take none but the outer and superficial part thereof. This we must be satisfied to call pure water; but even this is far short of the pure unmixed philosophical element-which, in reality, is no where to be found. As water is thus mixed with foreign matter, and often the repository of minute animals or vegetable seeds, we need not be surprised that, when carried to sea, it is always found to putrefy. But we must not suppose that it is the element itself which thus grows putrid and offensive, but the substances with which it is impregnated. It is true, the utmost precautions are taken to destroy all vegetable and animal substances that may have previously been lodged in it, by boiling; but, notwithstanding this, there are some that will still survive the operation, and others that find their way during the time of its stowage. Seamen assure us that their water is generally found to putrefy twice at least, and sometimes thrice, in a long voyage. In about a month after it has been at sea, when the bung is taken out of the cask, it sends up a noisome and dangerous vapour, which takes fire upon the application of a lighted candle. The whole body of the water is then found replete with little worm-like insects, which float with great briskness through all its parts. These generally live for about a couple of days; and then dying, by depositing their spoils for a while increase the putrefaction. time, the heavier parts of these sinking to the bottom, the lighter float in a scum at the top; and this is what the mariners call the water's purging itself. There is still, however, another race of insects, which are bred very probably from the spoils of the former, and produce, after some time, similar appearances; these dying, the water is then thought to change no more. However, it very often happens, especially in hot climates, that nothing can drive these nauseous insects from the ship's store of water. They often increase to a very disagreeable and frightful size, so as to deter the mariner, though parching with thirst, from tasting that cup which they have contaminated. After a dif This water, as thus described, is therefore a very ferent fluid from that simple elementary substance upon which philosophical theories have been founded, and concerning the nature of which there have been so many disputes. Elementary water is no way com. pounded, but is without taste, smell, or colour, and incapable of being discerned by any of the senses except the touch. This is the famous dissolvent of the chymists, into which, as they have boasted, they can reduce all bodies, and which makes up all other substances, only by putting on a different disguise. In some forms it is fluid, transparent, and evasive of the touch; in others, hard, firm, and elastic. In some it is stiffened by cold; in others, dissolved by fire. According to them, it only assumes external shapes from accidental causes; but the mountain is as much a body of water as the cake of ice that melts on its brow; and even the philosopher himself is composed of the same materials with the cloud or meteor which he contemplates. Speculation seldom rests when it begins. Others, disallowing the universality of this substance, will not allow that in a state of nature there is any such thing as water at all. "What assumes the appearance," say they, "is nothing more than melted ice. Ice is the real element of Nature's making; and when found in a state of fluidity it is then in a state of violence. substances are naturally hard; but some more readily melt with heat than others. It requires a great heat to melt iron-a smaller heat will melt copper; silver, gold, tin, and lead, melt with smaller still; ice, which is a body like the rest, melts with a very moderate warmth; and quicksilver melts with the smallest warmth of all. Water, therefore, is but ice kept in continual fusion, and still returning to its former state when the heat is taken away." Between these opposite opinions the controversy has been carried on with great ardour, and much has been written on both sides; and yet, when we come to examine the debate, it will probably terminate in this question-whether cold or heat first began their operations upon water. This is a fact of very little All importance, if known; and, what is more, it is a fact we can never know. Indeed, if we examine into the operations of cold and heat upon water, we shall find that they produce somewhat similar effects. Water dilates in its bulk by heat to a very considerable degree; and, what is more extraordinary, it is likewise dilated by cold in the same manner. same. If water be placed over a fire, it grows gradually larger in bulk as it becomes hot, until it begins to boil; after which no art can either increase its bulk or its heat. By increasing the fire, indeed, it may be more quickly evaporated away; but its heat and its bulk still continue the same. By the expanding of this fluid by heat, philosophers have found a way to determine the warmth or the coldness of other bodies; for if put into a glass tube, by its swelling and rising it shows the quantity of heat in the body to which it is applied; by its contracting and sinking, it shows the absence of the Instead of using water in this instrument, which is called a thermometer, they now make use of spirit of wine, which is not apt to freeze, and which is endued even with a greater expansion by heat than water. The instrument consists of nothing more than a hollow ball of glass, with a long tube growing out of it. This being partly filled with spirits of wine, tinctured red, so as to be seen when it rises, the ball is plunged into boil ing water, which, making the spirit within expand and rise in the tube, the water marks the greatest height to which it ascends; at this point the tube is to be broken off, and then hermetically sealed by melting the glass with a blow-pipe; a scale being placed by the side completes the thermometer. Now, as the fluid expands or condenses with heat or cold, it will rise and fall in the tube in proportion, and the degree or quantity of ascent or descent will be seen in the scale. No fire, as was said, can make water hotter after it begins to boil. We can therefore at any time be sure of an equable certain heat-which is that of boiling water, which is invariably the same. The certainty of such a heat is not less useful than the instrument that measures it. It affords a standard, fixed degree of heat over the whole world-boiling water being as hot in Greenland as upon the coasts of Guinea. One fire is more intense than another; of heat there are various degrees; but boiling water is a heat every where the same, and easily procurable. As heat thus expands water, so cold, when it is violent enough to freeze the same, produces exactly the same effect, and expands it likewise. Thus water is acted upon in the same manner by two opposite qualitiesbeing dilated by both. As a proof that it is dilated by cold, we have only to observe the ice floating on the surface of a pond, which it would not do were it not dilated, and grown more bulky by freezing than the water which remains unfroze. Mr. Boyle, however, put the matter past a doubt by a variety of experiments. Having poured a proper quantity of water into a strong earthen vessel, he exposed it, uncovered, to the open air in frosty nights, and observed that continually the ice reached higher than the water before it was frozen. He filled also a tube with water, and stopped both ends with wax; the water, when froze, was found to push out the stopples from both ends, and a rod of ice appeared at each end of the tube, which showed how much it was swollen by the cold within. From hence, therefore, we may be very certain of the cold's dilating of the water; and experience also shows, that the force of this expansion has been found as great as any which heat has been found to produce. The touchhole of a strong gun-barrel being stopped, and a plug of iron forcibly driven into the muzzle, after the barrel had been filled with water it was placed in a mixture of ice and salt; the plug, though soldered to the barrel, at first gave way, but being fixed in more firmly, within a quarter of an hour the gun-barrel burst with a loud noise, and blew up the cover of the box wherein it lay. Such is its force in an ordinary experiment. But it has been known to burst cannons, filled with water and then left to freeze; for the cold congealing the water, and the ice swelling, it became irresistible. The bursting of rocks by frost, which is frequent in the northern climates, and is sometimes seen in our own, is an equal proof of the expansion of congealed water. For having by some means insinuated itself into the body of the rock, it has remained there till the cold was sufficient to affect it by congelation. But when once frozen, no obstacle is able to confine it from dilating; and, if it can not otherwise find room, the rock must burst asunder. This alteration in the bulk of water might have served as a proof that it was capable of being compressed into a narrower space than it occupied before; but, till of late, water was held to be incompressible. The general opinion was, that no art whatsoever could squeeze into a narrower compass; that no power on earth, for instance, could force a pint of water into a vessel that held a hair's-breadth less than a pint. This, said they, appears from the famous Florentine experiment, as the water, rather than suffer compressure, was seen to ooze through the pores of the solid metal; and at length, making a cleft in the side, spun out with great vehemence. Later trials have proved that water is very compressible, and partakes of that elasticity which every other body possesses in some degree. Indeed, had not mankind been dazzled by the brilliancy of one inconclusive experiment, there were numerous reasons to convince them of its having the same properties with other substances. Ice, which is water in another state, is very elastic. A stone flung slantingly along the surface of a pond bounds from the water seve ral times, which shows it to be elastic also. But the trials of Mr. Canton have put this past all doubt; which, being somewhat similar to those of the great Boyle, who pressed it with weights properly applied, carry sufficient conviction. What has been hitherto related is chiefly applicable to the element of water alone; but its fluidity is a property that it possesses in common with several other substances, in other respects greatly differing from it. That quality which gives rise to the definition of a fluid namely, that its parts are in a continual intestine motion-seems extremely applicable to water. What the shapes of those parts are it would be vain to attempt to discover. Every trial only shows the futility of the attempt: all we find is that they are extremely minute, and that they roll over each other with the greatest ease. Some, indeed, from this property alone, have not hesitated to pronounce them globular; and we have in all our hydrostatical books pictures of these little globes in a state of sliding and rolling over each other. But all this is merely the work of imagination: we know that substances of any kind, reduced very small, assume a fluid appearance somewhat resembling that of water. Mr. Boyle, after finely powdering and sifting a little dry powder of plaster of Paris, put it in a vessel over the fire, where it soon began to boil like water, exhibiting all the motions and appearances of a boiling liquor. Although but a powder, the parts of which we know are very dif ferent from each other, and just as accident has formed them, yet it heaved in great waves, like water. Upon agitation, a heavy body will sink to the bottom, and a light one emerge to the top. There is no reason, then, to suppose the figure of the parts of water round, since we see their fluidity very well imitated by a composition the parts of which are of various forms and sizes. The shape of the parts of water, therefore, we must be content to continue ignorant of. All we know is, that earth, air, and fire conduce to separate the parts from each other. Earthy substances divide the parts from each other, and keep them asunder. This division may be so great, |