Water; called also alma. This word is variously derived; some say it is quasi a qua vivimus, because by it we exist, others quasi aqua from the smoothness of its surface; some, from for sound, from the noise it makes in running. Natural philosophers define water to be an insipid, ponderous, transparent, colourless, uninflammable, and highly fluid body, susceptible of the different states of aggregation from solidity to that of elastic vapour. It owes its fluidity to a certain degree of heat, since with a heat two-ihirds less than that of our blood it congeals; and with somewhat more than twice the heat of our blood it boils, beyond which it cannot be made hotter.

Water is more compressible in winter than in summer, contrary to most, if not all other fluids; it is also elastic. See Philos. Trans. vol. iii. p. 640.

It is found in almost every natural body; and nature unites it with many bodies which art in vain attempts to imitate. It exists in the hardest and most compact calcareous stones, and forms the greater part of the fluids, and a considerable proportion of the solid parts, of animal bodies. It is contained in bodies either in a state of simple mixture or of combination; in the first case it renders bodies humid, is perceptible to the eye, and may be disengaged with the greatest facility; in the second its own characters disappear. In this form it exists in crystals, salts, plants, animals, etc.: water imparts to many forms of bodies hardness and transparency, particularly to salts and many stony crystals. Some bodies are indebted to water for their fixity: the acids, for instance, are supposed to acquire fixity only by combining with water. It is now however proved to be a compound body, formed by the union of oxygen and hydrogen. On this subject our readers may consult the works of modern chemists, particularly Cavendish, Lavoisier, Fourcroy, Thompson, and Chap-tal. as we must consider it only in a dietetic and medical point of view.

Water, as it is the most ancient, so it is the best and most common fluid for drink, and ought to be esteemed the most commodious for the preservation of life and health; for not only all kinds of animals, but the greatest part of mankind, preserve life by drinking water alone. If moderately drunk it assists digestion, quenches thirst, cools the habit, dilutes the fluids, opens obstructions, dissolves viscidities, corrects acrimony, promotes the fluid secretions, and is-an universal vehicle for solid food. It is superior to all other liquids, because it is purer, more simple, and more fluid than other drinks. The more pure the water the better; and that is certainly the best which falls in rain, collected from high situations in the country, then boiled a little, and afterwards distilled, the half which comes over first only to be used. This, from its purity, is also recommended to all chemists where water is to be employed; but, indeed, such as nature affords is a proper drink for mankind, if there is no impregnation to the taste or smell of a person of common sensibility. The softer and purer waters, however, are to be preferred for use; though the harder waters, or such at are impregnated with selenites, or rather earthy matters, have not been discovered by any decisive clear evidence to have produced the bad effects ascribed to them.

In the pharmaceutical use of water we must however be more cautious. Even the purest rain water was found by Margraaf to contain a small portion of a mu-riated salt, and in large cities it generally contains some vitriolated salt. Distilled water should therefore be particularly employed in dissolving the pure kali, the pure ammonia, sal acetosellae, terra ponderosa salita, argentum nitratum, mercurius nitratus, mercu-rius sublimatus corrosivus, and acetatus, tartarum emeticum, hepar sulphuris, and antimonii.

Water dissolves salts; and an ounce of water at a mean temperature, that of 60 degrees of Fahrenheit, will dissolve of

Good water is known by readily mixing with soap without curdling, and by quickly boiling pease, and pulse, soft and tender; and it keeps best in large vessels, in cold places, and in earthen or glass jars.

Muddy water may be cleared by adding two or three grains of alum to each pint, and thus the water is not injured. If hard it may be rendered soft by adding a few grains of the salt of tartar to each pint, in proportion to its hardness, but it leaves a neutral scarcely less inconvenient.

River water is the best for short voyages; but the spring water is longer before it putrifies, and answers better for long ones.

Stagnant waters; water in which is much melted snow, ice, or dew; water from mines; such as rises in low flat lands, and particularly from springs which contain an unctuous or bituminous matter at the bottom; are bad: but good waters are obtained from springs which are on high lands consisting of gravel; from the clouds, by rain falling at a distance from great towns; from rivers and rivulets: but the distilled is the most pure, and a regular drinking of it would perhaps in some cases be as beneficial as some of the most celebrated mineral waters. See Dr. F. Clifton's Translation of Hippocrates, on Air, Water, and Situation. Cullen's Materia Medica. Hoffman's Systema Rationale. Chaptal's Chemistry.

AquA mulsa. See Hydromeli.