Antyllus says that there are many differences of airs: some arising from the season of the year; some from the changes of the moon; and some from the hour of the day or night; some from thickness or tenuity, motion or rest, or from the admixture of terrene exhalations. The sun, he adds, warms the body; but the moon rather humectates, and, therefore, she moistens the brain, and occasions the putrefaction of the flesh; renders the bodies of those who sleep in the open air more humid and obtuse; and, for the same cause, she induces epilepsy and heaviness of the head. Cold air, he says, produces plumpness, good nutrition, and the formation of fat; it promotes the growth of the body, and hence, the inhabitants of northern climates are remarked to possess this character. It is unsuitable, however, to all acute disorders; and is also improper for certain chronic diseases, such as consumption, cachexy, paralysis, apoplexy, and rheumatism. Warm air consumes the body, attenuating and wasting the system, but it is preferable to cold air for imparting vigour and agility; it tries the powers, is useful in affections of the nerves and chest, but not in those of other parts. Thick air has no other good property, except that it prevents the powers from being dissipated. Thin air is most conducive to health. The air of high situations is said by him to be more salubrious to all persons, except those labouring under diaphoresis or syncope, and the aged. The atmosphere of places near the sea, he remarks, is milder than that of inland parts. Places in the neighbourhood of marshes are at all times unhealthy; but, in summer, their atmosphere is pestilent. Those by a river side are cold and changeable. See more fully Stobæus. (Sermo xcix.) Hippocrates gives many interesting observations on the effect of climate, and the state of the atmosphere, in influencing the health; but they are delivered so much in detail, that my limits do not admit of my entering into an exposition of them. (De Aëre Aquis, Locis.) The account there given of the effects of stagnant water when used as drink is particularly deserving of attention. He says it produces diseases of the spleen, dropsies, and the like. See Coray’s edition of this treatise. Haly Abbas gives a very elaborate disquisition on this subject. He describes minutely the characters of salubrious airs, and the changes produced upon them by the seasons of the year, the state of the winds, the nature of countries, and the stars, that is to say, the sun and dog-star. (Theor. v.) See also Rhases (Contin. xxxiii); Avicenna (i, 2, 2.) SECT. L.—ON WATERS.