(From acidus, sour). Mineral waters that contain a brisk spirit, when unaccompa-nied with heat, are thus named: but if they are hot also, they are called thermit. In Paracelsus, Fontale acetosum is of the same import.

As to the antiquity of their use, see Galen, Coelius Aurelianus, Pliny, etc. who speak also of their virtues.

Hoffman and many authors highly extol them, whilst others observe that a pure water, on account of its simplicity, such as that from Malvern and Toplitz springs, is to be preferred both for drinking and for bathing; and that these may be well supplied by distilled rain, or any other water that is soft and pure. Objectors allege, that the medicinal qualities in these waters only quicken their operation as water, but contribute nothing further, and that solutions of the same materials are of equal efficacy: to which the best reply has been, that the mineral contents are often volatile, and more subtile than art can produce; and that, when the powers of nature are expiring, experience proves their efficacy by their success as a last resource.

From the qualities of their contents their use is easily determined. See Aquae Medicinales.

Bleeding, or purging, or both, are frequently prescribed before the use of mineral waters; but, except a plethora attends, they are unnecessary.. As these waters are designed to act, so rest or exercise must be advised: rest and a cool situation favour their diuretic tendency; exercise and a warm air determine them to the skin; with temperance and moderation in the regimen, these are the principal directions on which success depends.

Their brisk sparkling property is owing to the quantity of uncombined carbonic acid gas which they possess;

E2 and indeed to this, perhaps, is owing their chief use as medicine. To increase this gas when defective, or to communicate it where it is totally wanting, see Dr. Priestley's directions for impregnating water with fixt air.