fea is appointed to prevent its putrefaction ;-for it is a fact, that, in small quantities at least, fea-water the most strongly falted will putrefy; and those who have been long becalmed in fultry regions, have witneffed a fimilar difpofition in the ocean itself. On the other hand, it will be admitted, that this is no putrid difpofition in the water, but in that immense quantity of animal particles, which in fo many ages have replenished the very ocean. As to the degree of SALTNESS in the fea, it varies in the fame places at different feafons, fometimes at different depths; but in general is found faltest where the fun is vertical, and the water fuffers the feverest heat. It appears from some experiments, formerly made in a voyage from England to Bombay in the Eaft-Indies, that the weight of the fea-water was greatest, not precifely at the Equator, but where the fun was vertical, and confequently, as I just hinted, where the heat was greatest. The greatest weight of a definite quantity of fea-water, which was observed in failing from 28 degrees, north latitude, to the Cape of Good-Hope, which is about 34 degrees fouth latitude, in the months of May, June, and July, was at St. Jago iflaud, north latitude 15 degrees; and the leaft was at Teneriff island, north latitude 28. The weights of equal bulks of Thames water, of the fea-water at Teneriff and St. Jago, were 659-673-780 grains; the proportion of which numbers may be nearly thus expreffed.-Thames water 1000, -Teneriff fea-water 1022,-St. Jago fea-water 1184. By comparing thefe numbers with a table in the Philofophical 7 Tranfactions Tranfactions, exhibiting the comparative weight of equal bulks of fimple water, and of water impregnated with dif ferent portions of fea-falt, it may be conjectured, that the Teneriff fea-water contained about of falt, and the St. Jago water about of its weight of falt, fo that it was nearly, if not fully, faturated. This very great proportion of falt in the water at St. Jago, feems liable to objection; fince one-fourth of its weight of falt is full as much as is yielded by the best brine-pits in England, whofe waters, filtering through rocks of falt, may be supposed to be fully faturated. But it is impoffible to determine, whether fuch a caufe might be near, or have any influence on, the water examined as above. In general, fea-water poffeffes about to its weight of falt. And this And this proportion renders it by much more compact, more dense, and of ftronger refiftance than fresh-water, infomuch, that I have been told of deeply laden veffels, which having paffed the dangers of the fea, too heavy to float on a thinner fluid, funk in port. It has been debated whether water be coMPRESSIBLE: fome think they have compreffed it, fo that a body of water occupied lefs fpace than before; but it should seem that water fuffers but little compreffion, if any, and that if no deceptive appearances mifled thofe gentlemen who maintain the affirmative, yet so small is the effect produced by confiderable ftrength, that little stress can be laid upon it. But when we mention its ELASTICITY and EXPANSION, neither calculation nor imagination can determine its limits. X, Y y Water Water expands by heat; and, what is very extraordinary, it alfo expands by cold: no machine can be invented, no strength can be effectually applied to confine water while freezing. You have often noticed bottles and vials, full of water and clofely corked, if expofed to feverely cold weather, cracked and burften: were they made of iron, and an inch in thicknefs, they would experience the fame event; nay freezing water has been known to burst cannon. If we feek further proof of its power, it appears in thofe huge fragments of maffy rocks, which from time to time are separated from their parent mountains, and tumbled from their fummits: think of their weight, their folidity, their fize, then think of the caufe which difplaces them,—a little water, which having trickled through their fiffures, till united in fome hollow, is there frozen, and being frozen is dilated, and being dilated refufes to fuffer longer confinement, and, if room cannot otherwise be made for it, it will rend the very rock. But it is more ufual to notice the very great expanfive power of water, when by fire it is converted into fteam: and fince this affords to mankind a variety of useful machines, it may demand a little attention. I faid lately, that the weight of air used in working fome of the fire engines was fix or seven tons; this weight is raifed fixteen times in a minute with eafe, by a quantity of fteam introduced underneath it. This fteam is not fuch as might be, but little different, if at all, from that of a boiling tea-kettle. Yet we find that one cubic inch of water is expanded into 2900 inches of this fteam. Now the elasticity of fteam increafing with heat, and the fpace fpace it endeavours to occupy being proportionate to its elasticity; and fince, when equal in ftrength to the air, it occupies nearly 3,000 times its former fpace, were it fubmitted to yet greater heat, it might become five or fix times more expanfive, and occupy 15,000 or 20,000 times its former fpace. -This is at rather a low eftimation. The force of fteam is taken at three times the force of gunpowder. So far has skill employed this element in its fervice; and fo far we may depend on its powers. Advancing on these ideas, there have not been wanting thofe, who have endeavoured to account for the phenomena of earthquakes, by confidering them as water rarefied into steam by fubterraneous fires, and forcing a paffage in every direction, not impeded (effectually) by the folid earth itself. Water poffeffes, in common with all fluids, the property of rifing always to its level; fo that be the length of a pipe what it may, the fluid contained in it will ftand equally high at both ends. This is well known to those who have occafion to lay pipes over the fides of hills, &c. for if they can form a refervoir at a height fufficient, their bufinefs is over. And thus the water, diftributed through great part of London from the New-River, after defcending into the town, would, of its own accord, mount into every ciftern not higher than the eminence from whence it took its departure. It is true, means are found to make it mount higher; but this is not its natural inclination, but the effect of art. The fame art appears in that useful machine the pump, wherein we fee the water rise much above the level of the fpring which furnishes it. This is merely the refult of the weight of the air, which being taken off beneath the pump, while the other parts of the water's furface are exposed to it, the fluid naturally takes refuge where it meets least resistance; and this effect follows, to fuch a height of water as counterbalances the preffure of the atmosphere, i. e. about thirty-two or thirty-three feet. Water preffes according to its perpendicular height: fo that the fame quantity of liquor which is one foot high, and three inches in diameter, if rendered only one inch in diameter, and confequently three feet high, acquires great increase of power by the alteration; and if it was reduced to half an inch in diameter, and fix feet high, it would become yet more powerful, On this principle a pint of water may burft a hogfhead; for if the hogfhead be full, and the pipe through which the pint of water, attempted to be introduced, be of fufficient height, the weight of the water will make its way, and the veffel, unable to contain it, muft yield to its preffure. There is a very ftrange peculiarity of water, by which it rifes in very small glafs tubes without preffure, and fimply of its own accord. If a glafs tube have two curved legs (turning upward) one only a quarter of the diameter of the other, the water will always ftand higheft in the narroweft: if the dif proportion be yet greater, the difference will be greater alfo This phenomenon has puzzled the moft fagacious obfervers; the attraction of the glafs to the particles of water, which is predominant and effectual where there is the greateft quantity of glafs and leaft water, feems to bid faireft for folving the difficulty, Water |