pered together, produce a mass, scarcely inferior, in point of solidity, to the primitive limestone.Many, if not most, of the effects here ascribed to water, in uniting and consolidating the parts of various bodies, have been attributed, by modern chemists and philosophers, to the gas, or fixable air, which enters into their composition; which escapes when they are dissolved, and which is capable, in certain circumstances, of being again restored to them.

Although water be defined a fluid, it has been ⚫a controverted point among philosophers, whether fluidity be its natural state, or the effect of violence. We sometimes find it appear in a fluid and sometimes in a solid form; and as the former, in our warmer climate, is the more common, we conclude it to be the proper one, and ascribe the other to the extraneous action of cold. Boerhaave, however, asserts the contrary, and maintains water to be naturally of the crystalline kind; since, wherever a certain degree of fire is wanting to keep it in fusion, it readily grows into a hard substance, under the denomination of ice. Boyle is much of the same opinion. Ice, he observes, is commonly reputed to be water brought into a preternatural state by cold; but with regard to the nature of things, and setting aside our arbitrary ideas, it might be as justly said, that water is ice preternaturally thawed by heat. If it be urged, that ice left to itself, will, upon the removal of the freezing agents, return to water, it may be answered, that, not to mention the snow and ice which lie, during the whole summer, on the Alps, and other high mountains, even in the torrid zone, we have been assured, that, in some parts of Siberia, the surface of the ground continues more months in the year frozen by the natural temperature of the climate, than thawed by the heat of

the sun; and, a little below the surface of the ground, the water that may happen to be lodged in the cavities there continues in a state of ice all the year round so that, in the heat of summer, when the fields are covered with corn, if you dig a foot or two deep, you will find ice, and a frozen soil.

Water, if it could be had clear and pure, Boerhaave observes, would have all the requisites of an element, and be as simple as fire; but no expedient has hitherto been discovered for procuring it so pure. Rain-water, which seems the purest of all those we know of, is replete with numberless exhalations of all kinds, which it imbibes from the air; so that, if filtered and distilled a thousand times, feces still remain. The rainwater, moreover, gathered from the roofs of houses, is a lixivium of the salt of tiles, slate, and the like, impregnated with the dungs and feces of the animals, birds, &c. deposited thereon, and the exhalations of numerous other things. It may be added, that all the rain-water gathered in cities must, at least, be saturated with the smoke of a thousand chimnies, and the various effluvia of a number of persons, &c. Besides this, fire is contained in all water; as appears from its fluidity, which is owing to fire alone.

As what is in the air necessarily mixes itself with water, it hence appears impossible to have such a thing as pure water. If you percolate it through sand, or squeeze it through pumice, or pass it through any other body of the same kind, you will always have salt remaining. Even distillation cannot render it pure; for it leaves air therein, which necessarily abounds in corpuscles of all sorts.

The water that flows within, or upon the surface of the earth, contains various earthy, saline, metallic, vegetable, or animal particles, according

to the substances over or through which they pass.

The purest of all waters we can any way obtain, is that distilled from snow, gathered in a clear, still, pinching night, in some very high place; taking none but the outer or superficial part of it. But a number of repeated distillations, the greatest part of the earth, and other feces, may be separated from this: and this is what we must be contented to call pure water. In a word, it is the opinion of Boerhaave, that no person ever saw a drop of pure water: that the utmost of its purity known, amounts only to its being free from this or that sort of matter; that it can never, for instance, be quite deprived of salt; since air will always accompany it, and air always contains salts,

Many of the most eminent chemists have made experiments, in order to ascertain the conversion of water into earth. Boyle relates, that an ounce of water, distilled carefully in glass vessels two hundred times, yielded six drams of a white, light, insipid earth, fixed in the air, and indissoluble in water. Hence he concludes, that the whole water, by further prosecuting the operation, might be converted into earth. Godfrey, and others, concur in this opinion; but Boerhaave (who attributes the earth obtained by Boyle to the dust floating in the air, and to the instruments employed in the operation) is supported by Macquer, and others, in maintaining, that pure water is unalterable, and incapable of being decomposed; so that, whatever be the substances with which it is combined, when separated from these and sufficiently purified (and also when distilled singly, or mixed with other substances), its nature and essential properties still remain unchanged.

Water seems to be diffused every where, and to be present in all space, where there is matter. There are few bodies in nature that will not yield

water; and it is even asserted, that fire itself is not without it. Among other remarkable circumstances, it has been observed, that bones dead and dried twenty-five years, and thus become almost as hard as iron, have yet, by distillation, afforded half their weight of water.

Water is a very volatile body; it is entirely reduced into vapour, and dissipated, when exposed to the fire and unconfined. Heated in an open vessel, it has been observed to acquire no more than a certain determinate degree of heat, how intense soever the fire to which it is exposed; and this greatest degree of heat is that which it has at the moment before it begins to boil.

It was formerly imagined, that water was incompressible, and therefore non-elastic; an opihion, founded on the famous Florentine experiment already mentioned, as proving its penetrative power. But the validity of the inferences drawn from this experiment have been justly questioned; Mr. Canton having proved, by very accurate experiments, that water actually is compressed by the weight of the atmosphere.

But, not to be too diffusive on this subject, I shall endeavour to state concisely the nature of the component particles of water, and then its various uses.

First: the particles of water are, as to our senses, infinitely small, whence their penetrative power. 2. Very smooth and slippery, or void of any sensible asperities. 3. Extremely solid. 4. Perfectly transparent, and as such invisible'. 5. If water be considered as consisting of spherical

Pure water, inclosed in a vessel hermetically sealed, projects no shadow, so that the eye cannot discover whether the vessel have water in it or not; besides, the crystals of salts, when the water is separated from them, lose their transparency.

or cubical particles, hollow within-side, and of a firm texture, here will be enough to account for the difficulty of compressing it, and also for its being light, fluid, and volatile; its firmness and similarity will make it resist sufficiently; and its vacuity renders it light enough, &c. And the little contact between spherules (if, indeed, they touch at all) will account for the weakness of its cohesion. 6. Water is the most insipid of all bodies; the taste we sometimes observe therein not arising from the mere water, but from salt, vitriol, or other bodies mixed with it. And, lastly, it is perfectly inodorous, and void of the least smell.

The uses of water are infinite; in food, medicine, agriculture, navigation, and many of the arts. As a food, it is one of the most universal drinks in the world; and, if we may credit many of our latest and most judicious physicians, it is also one of the best. As a medicine, it is found internally a powerful febrifuge; and excellent against colds, coughs, the stone, scurvy, &c. Externally, its effects are not less considerable. In agriculture and gardening, water is allowed absolutely necessary to vegetation. Many naturalists have even maintained it to be the vegetable matter, or the only proper food of plants; but Dr. Woodward has overturned that opinion, and en deavoured to show, that the office of water in vegetation is only to be a vehicle to a terrestrial matter, of which vegetables are formed, and that it does not itself make any addition to them. Water is of the utmost use in chemistry, being one of the great instruments by which all its operations are performed; and it is of the greatest service in many of the mechanical arts and ordinary occasions of life.