yet been discovered, which may warrant our afferting that we poffefs water entirely pure; and it is probable, when such a discovery shall be made that (like air), more forts than one may be found. This is certain, as various airs by commixture are rendered fit for the fupport of animals, and as without fuch circumftance air would be ufelefs or noxious; fo the element of water, in the ftate nature offers it, is most fitted for the ufe of thofe who are to profit by it. We have already feen that vegetables fuffer by too great purity of water; and the fame effects, in a confiderable degree at leaft, might be thought to follow, were any perfon to drink distilled water only.

Of the wholesomeness of water, experience must be judge, fince the inhabitants of different places find that to which they have been accustomed (and which fometimes. looks far from inviting to a stranger), both agreeable and healthful.

It is common to put water to the teft, by trying whether it will form a lather with foap, or whether it will curdle ; and this is thought a diftinction between hard water, as it is termed, and foft water. But hard water becomes like foft water upon expofure to the air. Those waters are in general lightest which have fewest diffolutions floating in them, but no water is to be obtained without fome, according to the ftrata through which it has run and I well remember, having procured fpecimens of water from feveral fprings in different parts of London, all of them extremely

X

Xx

clear,

clear, yet each of them precipitated a sediment on the addition of a very small portion of acid of fugar. This is the origin of all mineral and medical baths, whofe waters, in their paffage through beds of metal, of fulphur, of arfenic, &c. diffolve a part of the mineral through which they run, and imbibing it, convey it to where they fpring; that these should have fome qualities which we cannot by art give to water, not wonderful, when we confider the unknown and unfuppofable combinations of minerals in any one bed; to which we may add, that by paffing through fucceffive beds of different forts, fomewhat may be loft, and a different somewhat gained. But of late, the qualities of the most celebrated waters have been closely imitated, and by the addition of various kinds of air (principally), the fame tafte, colour, and (fome fay) effects, are produced: nay it is not uncommon to make medical waters stronger of fimilar principles, than waters of the natural fprings which are imitated.

Transparency is a very agreeable quality in water, yet must not be relied on as a proof of falubrity, fince fea-water is at least as tranfparent as any. River water is thought, upon the whole, the lighteft; but we know, that in their courses, rivers receive many pollutions from various quarters; efpecially if the courfe of the ftream be through low and marshy lands; or if the course of any of those smaller streams, by which it is enlarged, be through fuch a channel. A river becomes in its progress more polluted than higher up the country, because it receives a stronger tincture from the

much

much greater quantity of plants, of minerals, of insects, of animals, &c. than is corrected by its increase of water: and those who live at the mouths of great rivers, and drink their waters, are faid to be unhappy proofs of this, and fubject to many difeafes in confequence.

The water of the river Thames is confidered as fuperior to all other for keeping at fea; but even this water has many. impurities abounding in it; but what I have heard afferted, feems I think strange, that water taken up below LondonBridge, with all the pollution of the city in it, is preferable to, and keeps better than if taken up above the Bridge. Shall we say that this pollution falls to the bottom, and carries with it much that is worfe? or that it contributes to kill many of those infects with which all water abounds? Certain it is, that all water by long keeping putrefies, and this most probably, by reafon of thofe minute infects, or vegetable feeds, which abound in it. But we must not fuppofe that it is the element itself, which thus grows putrid and offenfive, but the fubftances 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 fome that will still furvive the operation; and others find their way during the time of its ftowage. Seamen, therefore, affure us, that their water is generally found to putrefy twice, at least, and fometimes three times, in a long voyage. In about a month after it has been at fea, when

the

the bung is taken out of the cafk, it fends up a noisome and dangerous vapour, which would take fire upon the application of a candle. The whole body of the water then is found replete with little worm-like infects, that float, with great brifknefs, through all its parts. Thefe generally live for about a couple of days; and then dying, by depofiting their fpoils, for a while increase the putrefaction. After a time, the heavier parts of these finking to the bottom, the lighter float, in a scum, at the top; and this is what the mariners call, the water's purging itfelf. There are ftill, however, another race of infects, which are bred, very probably, from the fpoils of the former; and produce, after' fome time, fimilar appearances: thefe dying, the water is then thought to change no more. However, it very often happens, efpecially in hot climates, that nothing can drive these naufeous infects from the fhip's ftore of water. They often increase to a very difagreeable and frightful fize, so as to deter the mariner, though parching with thirft, from tasting that cup which they have contaminated.

RAIN-WATER is a fluid of Nature's own diftillation, of whofe causes we have treated; it is more friendly and nutritive to plants than any other; but where rain-water only is ufed by mankind, it is by no means the most falubrious though, perhaps, its infalubrity is in great part often attributable to the refervoirs wherein it is kept, and to over-long keeping.

SNOW-WATER is drank chiefly, if not altogether, at the feet

of

of the Alps, and many other mountains; in Greenland, and in fome parts of England: to the drinking this water has been attributed those very large, I might fay frightful, wens, or fwellings, which disfigure the throats, &c. of the inhabitants in fome places. But this opinion feems erroneous; as they are totally unknown in Greenland, and are common in Sumatra, where fnow is a phenomenon which never occurs.

SEA-WATER is diftinguished by its faltnefs; and this property of fea-water has long excited the opinions of the learned, and of courfe has long divided them.-Some think, the rivers imbibing fomewhat of faltnefs from bodies over which they flow, or which they bring down to the sea, might in time, by leaving falts in the fea, render it falt: while others maintain, that the fea was formerly falter than at prefent, fo great an influx of fresh-water gradually affecting the ocean: a contradictory mode of reafoning from the former, but equally void of demonstration or plaufibility. A third party hint at rocks of falt, fitly difpofed to be diffolved by the waters (and fuch we know there are); while thofe who think the water was created originally falt, have much to urge in fupport of the fentiment. And probably its degree of faltness was not very different from what we now find it, for it feems, that though certain kinds of fishes are adapted to fresh-water, yet their numbers bear little proportion to thofe who conftantly inhabit falt-water, and who cannot exift out of it. If, therefore, thefe fishes poffeffed at firft the fame natures as now, their element was of neceffity falt: this queftion feems therefore decided, without enquiring how far the faltnefs of the

fea