There are, in the neighbourhood of London, many springs of similar quality to this of Epsom: of these the principal are at Acton, Kilburne, Bagnigge Wells, and formerly the Dog and Duck in St. George’s Fields; but they are, in general, so weak as to render very large quantities of the water necessary to produce any sufficient medical effect. 7. HIGHLY CARBONATED ALKALINE WATER. 291. _SELTZER WATER is an highly carbonated alkaline water. When fresh, or well preserved, it is perfectly clear, and sparkles much when poured into a glass. It is somewhat pungent, slightly saline, and a little alkaline to the taste._ _It contains chalk, carbonat of magnesia, carbonat of soda (201), and common salt; and more carbonic acid gas, or fixed_ _air (26), than any water hitherto known. It is hard, and curdles with soap._ The spring which supplies this water is situated in Nieder Seltzer, a village in a fine woody country, within the bishopric of Treves; and there are few mineral springs which have acquired so much celebrity for medical virtues as this. The diseases, for the removal of which it has been successfully applied, are too numerous to be here particularized. To the taste it is very agreeable, and when drunk in moderate quantity, it exhilarates the spirits, increases the appetite, and produces no particular determination to the bowels. It is to the strong impregnation with carbonic acid, and the small proportion of soda which it contains, that its most important benefits are owing. If it be closely corked and sealed, Seltzer water may be kept without injury, or even alteration, for a very considerable time; but, if exposed to the air, it soon becomes fetid. It is used as a common drink at table in many parts of Germany and Holland, and is even brought into England in stone bottles, each containing about three pints. A large proportion of Seltzer water, either genuine or artificial, is consumed in this country. 8. CHALYBEATE WATERS. 292. Are such as contain a portion of iron. This is easily detected by the property which it has of striking a black colour with tincture of nutgalls. 293. _TUNBRIDGE WATER is a carbonated chalybeate, the small portion of iron which it contains being held in solution by carbonic acid (26). It is, however, neither brisk nor acidulous. To the taste it is simply chalybeate; and that only in a slight degree._ _Its foreign contents are oxide of iron (21), a small portion of common salt, muriat of magnesia, and sulphat of lime (192), carbonic acid gas or fixed air (26), and other gases, but these only in small quantity._