produces, both on animals and vegetables, ought to be attributed*.

Water, though apparently a simple fluid, is composed of two gases, oxygen and hydrogen; about six parts of the former to one of the latter.

The following signs of good and bad water are extracted from Vitruvius, and other authors who have entered into that investigation †.

Signs of good Water.-1. It may be inferred, from the vigour and florid looks of the inhabitants, and from the healthiness of the animals living in the neighbourhood, that the waters they use are good in quality. 2. Also when a few drops of salubrious water are let fall on good copper, and they occasion no spot thereon. 3. Good water is found fit for boiling vegetables quickly, in particular, pease, beans, and other pulse. 4. Good waters are light; and perhaps lightness of water is the most positive token of its goodness, and its exemption from other ingredients. 5. Those waters which dissolve soap in the completest manner, are generally excellent. 6. Springs issuing from sandy soils, sandstone, gravel, and redstone, are usually wholesome. 7. Good water is soft, and totally free from smell. 8. Good water easily acquires the taste, colour, and flavour that is wished to be given to it. 9. Springs which freeze with difficulty, and suffer little variation in their temperature, at different seasons of the year, are deemed good. 10. Water of good quality soon grows warm by the heat of the fire, and soon cools when exposed to the air. 11. It is reckoned a good sign of river-water, when fresh verdure is observed along the banks where it runs. 12. Waters are good which produce water-cresses and water-marigolds. 13. If fresh waters rather abound with fish, in particular, if the fish appear healthy, and are found well tasted, it indicates, that the water which they inhabit may be used in diet.

Signs of bad Water.-1. Where the people are pale and unhealthy; and, in particular where they are troubled with swellings in the throat. 2. Where the water, in a boiling state, will not soften pease and beans, and other pulse. 3. Where it has ferruginous or vitriolic qualities. 4. In general, waters which issue from peat-mosses. 5. Where they have a petrifying quality, or are much impregnated

Thomson's System of Chemistry, vol. iii. p. 427. Mr. Henry found that 100 cubic inches of spring water contained 3.38 inches of carbonic acid, and 1.38 of atmospheric air.

In particular, a work entitled, De L'Eau, relativement à l'Economie Rustique, par M. Bertrand, &c. Lyon, 1764.

with calcareous earth: And, 6. Where they are full of saline or sulphureous particles. Indeed, mineral waters are not proper as common diluents, though useful as medicine.

It has been disputed, whether what is called hard water, or the sort which has some acid, or calcareous matter in solution, and which is unfit for being used with soap*, can with safety be taken as drink.

There are probably few, who would not give a preference to soft, over hard water, for general use; at the same time, the authorities in favour of hard water, and the proofs adduced in its behalf, are so very satisfactory, that persons who have no other water to which they can easily have access, need not, on that account, entertain any apprehensions of danger from using it†.

Water may be divided into two kinds, Common and Mineral.

By common water, naturalists understand that which has no perceptible distinguishing taste or smell, and which exerts no particular or sensible effect on the human body, when internally taken. Such water is peculiarly well calculated for diet.

Mineral waters, on the other hand, have properties directly contrary, and as they are never, except from necessity, used as aliment, they do not come within the scope of the present enquiry.

Common waters may be considered under the following general heads: 1. Rain. 2. Snow. 3. Hail. 4. Ice. 5. Spring. 6. Well. 7. River. 8. Lake. 9. Marsh; and, 10. Pond water; to which will be added, some observations on the rendering sea-water fit for being used in diet.

1. Rain-water.-In favourable circumstances, at a distance from the smoke of cities or towns, rain-water ought to be as free from foreign ingredients, as any that has not undergone the process of distillation. But when there are heterogeneous particles in the atmosphere, the rain must imbibe them.

To obtain rain-water in its greatest purity, it should, as Neumann directs, be collected either on the tops of mountains, or in open plains, and not when the rain begins, but after

• When soap is put into such water, its alkali is immediately attracted by the acid of the water, the soap is decomposed, and the oil of it swims on the surface of the water.- Encycloped. Brit. vol. xviii. p. 811.

+ Cullen, in his Materia Medica; Darwin in his Zoonomia; Saunders in his Treatise on Mineral Waters; and Peacock, in his Observations on the Sulphur Baths at Dimsdale, in the county of Durham, are all of that opinion.

a considerable quantity has fallen. The winter, or very early in the spring, is esteemed the best season of the year for obtaining pure rain-water. The rain, also, which falls after a long tract of wet weather, must be pure, for the atmosphere is then, in some measure, washed, if that expression may be made use of, from all extraneous substances. When collected in this manner, boiling is unnecessary, with a view to purify it.

2. Snow-water.-In certain cold climates, and in high latitudes, thawed snow forms the constant drink of the inhabitants during the winter season. In the Alps, where this is necessarily the case, many of the inhabitants are deformed with swellings in the neck, which have been often imputed to the use of snow-water; but it is now ascertained, that such swellings are owing to the Tufa, a volcanic substance. Indeed, the same disease is frequent in Sumatra, where ice and snow are never seen, and quite unknown in Chili and Thibet, though the rivers of these countries are chiefly supplied by the melting of the snow, with which the mountains are covered. When immediately melted, snow-water contains no air, as that substance is expelled during freezing, consequently, it is remarkably vapid, but it soon recovers the air it had lost, by exposure to the atmosphere *. If made from snow that falls in calm weather, it is the purest of any, next to distilled water, and will keep good for many years. It will also dissolve soap better, and will sooner boil and cool again, than almost any othert.

3. Hail-water.-Among the various sorts of water, that from melted hail ought to be peculiarly pure; for the lightest parts of water ascend to the highest regions, and are there congealed, (without any kind of mixture with other particles), into one homogeneous substance, and put into a form, which cannot easily partake of impurities in its descent.

4. Ice-water.-Ice may either be formed from fresh or salt water. As to the first, we find it placed by Celsus,

From its want of air, no fish can live in snow-water, until it has been exposed to the atmosphere.

Burton's Treatise on the Non-Naturals, p. 238. Barry, in his Observations on the Wines of the Ancients, p. 392, states, that from experiments 'which have been made on water, collected from the purest snow dissolved on the highest mountains, and the best common water, it appears, that the former possessed several peculiar qualities, which must render it more salutary as a beverage.

Burton's Treatises on the Non-Naturals, p. 237.-Also, Willich's Lectures on Diet, &c. p. 392.

in the fifth rank in regard to wholesomeness, or after rain, spring, river, and well-water*. As to the second sort, in a work written many years ago, by a Danish author, (Bartholinus, de nivis usu), it is stated, that if the ice of seawater be thawed, it is found to have no saltness, which was ascertained by a professor in the University of Copenhagen; and a British writer, whose work was published in the year 1738, takes notice of that circumstance, and adds, that thawed ice, from sea- water, is often used at Amsterdam for brewing +.

5. Spring-water-Under this general head are comprehended, all those waters that arise from any depth to the surface of the earth, and are used, either at the fountainhead, where they spring, or at least before they have mixed with other waters. These certainly ought to be as pure as rain-water, from which they generally originate, being in a manner filtrated in the earth, if it were not, that in their passage through the soil, they meet with various soluble bodies, and hence are impregnated with mineral and other particles. The best are such as flow from gravel or fine white sand. Springs in a clay soil generally produce hard water, unfit for several uses.

6. Well-water. Where springs are not to be met with, it is often necessary to dig deep pits into the bowels of the earth, for the purpose of finding water; and where the quantity is not sufficient to overflow the mouth of the well, pumps and other means are used for the purpose of raising the water to the surface. Well, or pump water, must greatly resemble spring-water, being derived from the same source; but it is more liable to be impregnated with foreign ingredients, in consequence of its stagnation and slow filtration; hence, the more frequently that the well is used the better. The water of wells not in sandy or gravelly soils, has often the advantage of containing a greater quantity of fixed air, or carbonic acid gast. In some places, they have dug wells

Grieve's Celsus, p. 97.

+ Burton's Treatise on the Non-Naturals, p. 238. Sir John Pringle, there fore, in his discourse on some late improvements upon the means of preserv ing the health of mariners, p. 34, was mistaken in supposing, that the cele brated Cook was the first who discovered that frozen sea-water thawed into fresh. The fact is, that the salt does not freeze, the frost only affecting the fresh particles of salt-water.

Thomson's System of Chemistry, vol. iii. p. 429. There are many useful works on well, or pump-water, as Heberden's Observations on the pumpwater of London, (Medical Transactions, vol. i.); Percival's on that of Manchester; and Falconer's on that of Bath. Dr. Heberden asserts, that most of the pump-waters used in London contain lime, and the three mineral acids of vitriol, nitre, and sea-salt, besides an oiliness, which discolours them, and gives them a remarkably yellowish cast, when compared with

to no less a depth than 500 feet, and been amply repaid for the trouble and expence, by the purity of water thus attained. In consequence of a well having been sunk to nearly the depth above mentioned, and good water procured, the inhabitants of the parish of Steeple, in Dengy hundred, Essex, derived the greatest benefit to their health. 7. River-water.-There are certainly some objections to the water of rivers, from the impurities of the springs, or other fluids of which the water is composed, and from the substances thrown into it; yet, on the whole, there is no water better calculated for general use. Indeed, where their motion is rapid, and their bed either gravel or silicious sand, they are said to be purer than even spring. water, depositing every thing during their course, which was merely mechanically supended. Some rivers, however, like the Thames, in passing through rich and cultivated plains, or populous towns and cities, become considerably charged with foreign matter. Such water is easily improved by filtration; or when left to settle, will become as clear as spring-water. Hence, the water of the Thames is preferred for long voyages even to spring-water*.

8. Lake-water.-The water of lakes is merely a collection of rain and snow water, spring-water, and riverwater, and of course must be impregnated with the same heterogeneous substances which they contain. It is seldom so transparent as river-water; but as the water of lakes is not so much agitated as that of rivers, any noxious substances frequently subside to the bottom, and do not injure the surface. An excellent mode of filtration is adopted by those who live on the borders of Loch Lomond, the largest and most beautiful lake in Scotland. Instead of taking it from the lake itself, they make a pit or hollow in any bank of gravel on its margin, into which the water naturally flows, cleared from any injurious particles.

pure distilled water. They are also liable to be tainted, in their passage under ground, by various inpurities, so frequent in the neighbourhood of so large a city. The nitrous acid in these waters makes the flesh boiled in them to become red. The tea and coffee infused in them are not palatable; and several physicians suspect, that they occasion many disorders, more especially among the infirm and children. There is also a work on pumpwater, recently published by Dr. Lambe, which merits attention, though he seems to carry his apprehensions, regarding the unwholesomeness of pump-water, much too far.

See Thomson's System of Chemistry, vol. iii. p. 428. Hooper's Lexicon, &c. Dr. Heherden states, that if two or three grains of alum are dissolved in a quart of thick river water, it makes the dirt very soon colfect, and slowly to precipitate: If then filtrated, it is immediately prepared

for use.