The water is so hard as instantly to curdle soap. It is considered useful in cases of debility, indigestion, and such diseases for which chalybeate and tonic remedies are required. The sea─bathing at Brighton is, in many cases, an additional and important advantage to those persons who use the chalybeate water. 9. COLD SULPHUREOUS WATERS. 298. HEPATIC, or SULPHUREOUS WATERS, are so strongly impregnated with sulphur, united either to hydrogen (45), or to an alkali, or both, as thereby to acquire a very sensible smell and taste. They have the property of blacking silver and lead; and are immediately known by the smell, which is very fetid, and like that which arises from the scouring of a foul gun─barrel, or, as some persons suppose, like the smell of rotten eggs. The taste of these waters is peculiar, and rather sweetish. They constitute a drink which, at first, is very unpalatable, but which, by habit, is soon reconciled to the drinker. None of them will bear carriage to any distance. 299. _HARROWGATE WATER is a cold sulphureous water, which has a very strong and fetid smell, like that of a damp rusty gun─barrel. To the taste it is bitter, nauseous, and strongly saline._ _Its foreign contents are common salt, muriat of lime, muriat of magnesia, chalk, carbonat of magnesia, Epsom salt (199), carbonic acid gas, or fixed air (26), azotic gas, and sulphureted hydrogen gas._ There are, at Harrowgate, four distinct sulphureous springs, which appear to have their rise in a large bog, at a small distance from the wells. The water of all these springs is similar in its properties and its distinguishing characters, but as one of them is more strongly impregnated with sulphur than the others, this alone is used for drinking, whilst the other three are employed to supply the baths. When the water of the former of these springs is first taken up, it is perfectly clear and transparent; and sends forth a few air─bubbles. Notwithstanding both its nauseous smell and taste, such is the power of habit in reconciling it to the palate, that, after a little while, nearly all persons who drink this water do it without disgust. When exposed to the air it loses its transparency, and assumes a somewhat greenish colour: the sulphureous odour abates; and, at last, the sulphur is deposited on the bottom and sides of the vessel in which it is kept. Such is the nature of Harrowgate water that a secret correspondence has often been carried on by means of it. A letter written with solution of sugar of lead is illegible; but if dipped into this water the writing will not merely become visible, but, in a short time, will appear almost black. Hydrogen has the property of reviving the metallic oxides: hence also it is that ladies who have used metallic cosmetics have become of a dark tawny colour by bathing in these waters.