Niederselters, in Nassau; the Carlsbad Springs in Bohemia; the Sweet Springs in Monroe county, Virginia, &c. .

The sulphureous waters are impregnated with sulphuretted hydrogen. They are distinguished by their ́odor, and by their causing a piece of silver immersed in them to turn black. Beside sulphuretted hydrogen, they contain alkaline and earthy sulphates and muriates, and they may be subdivided into two kinds; those which have sulphuretted hydrogen in a free state, and those in which it is combined with an alkali or an earth. The general effects of these waters are stimulant, and they are more often used in the form of a bath than internally. They are serviceable in gout and rheumatism, in sprains and bruises, in cutaneous disorders, &c.

Among the sulphureous springs may be mentioned those of Aix-la-Chapelle, in Rhenish Prussia; of Enghien, in France; of Harrowgate, in England; of Moffat, in Scotland; the White Sulphur Springs of Greenbrier county, the Red Sulphur of Giles county, and the Salt Sulphur of Monroe county, Virginia; the Olympian Springs and the Blue Licks, in Kentucky, &c.

Chalybeate waters contain iron, and are known by their peculiar taste, and by their becoming black when mixed with an infusion of nutgalls. In some, the iron is combined with sulphuric acid, in more with carbonic acid; when this is in excess, the waters possess acid properties, and form acidulous chalybeate waters.

Chalybeate waters are tonic and aperient, and are used with advantage in cases of debility and chronic diseases. Among the most noted springs of this class

are those of Tunbridge and Brighton, in England; of Spa, in Belgium; of Pyrmont, in Waldeck; the fourteen springs of Langenschwalbach, in Nassau; the springs of Ballston; Bedford, York, and Brandy wine Springs, in Pennsylvania; the Yellow Spring, in Ohio, &c.

Saline waters are those which contain the saline ingredients generally found in mineral waters, but which have very little or no iron or sulphuretted hydrogen, and have not carbonic acid in excess. These are subdivided into alkaline, containing alkali in a free state, or combined with carbonic acid; hard waters, or those which contain carbonate or sulphate of lime; salt waters, in which salt abounds; and purgative waters, which contain chiefly sulphate of magnesia, or Epsom salt.

The most celebrated thermal saline waters are those of Bath, Buxton, and Bristol, in England; of Dunblane and Pitcaithley, in Scotland; Plombieres and BourbonLancy, in France; Carlsbad and Teplitz, in Germany; Lucca and St. Julian, in Italy; and the Warm Springs of North Carolina.

Among the cold saline springs are those of Saratoga, in New York, and of Harrodsburg and Grenville, in Kentucky; Epsom and Cheltenham, Leamington, Scarborough, and Malvern, in England; and Sedlitz and Seidschutz, in Bohemia. When there is a considerable quantity of carbonic acid, they become more grateful to the taste, and when iron is present, as is sometimes the case, they acquire tonic and stimulant powers.

Thermal waters include individual springs of all the classes; a thermal spring being one which, whatever are its chemical properties, possesses a temper ature more or less elevated above that of the region in

which it is situated, and the changes of which do not coincide with those of the external atmosphere.

136

In

LAKES. A lake is an inlaid body of water not connected with the ocean or any of its branches. regard to the position of their beds, there are two classes of lakes; those formed in deep hollows among the mountains, and fed by springs or torrents; and those formed in level countries by the surplus water of rivers or in consequence of the want of a general declivity in the ground. Thus there is a system of the former class in the great Alpine girdle of the old continent, including the lakes of the Pyrenees, the Alps, the Apennines, and those of the Taurus, Caucasus, and Altaic chains; to the north of this great mountain band are the numerous lakes of the vast Northern plain of Europe and Asia, belonging to the latter class, and comprising the numerous lakes of Prussia, Sweden, Russia, and Siberia; to the south of the mountainous zone, in Africa, for instance, the lakes are few.

There is a similar disposition in the New World; a chain of mountain lakes accompanies the Andes through their whole course, including Titicaca, Nicaragua, Chapala, the small lakes of the Mexican valley, Timpanogos, &c., and while the great eastern plains of South America are nearly destitute of them, the regions around the Hudson contain an astonishing number of lakes, corresponding in number, character, and geographical situation to those which skirt the shores of the Baltic and the Frozen Ocean.

Another division of lakes is founded upon the manner in which they receive or discharge their waters, and in this point of view they form four classes: -1. Those which receive streams of water, and have an outlet to the ocean are the most numero is and extensive 2. Those which receive rivers, without having any visi

ble outlet, such as the Caspian Sea, Lake Tchad, in the interior of Africa, &c. 3. Those which receive no running water, but have an outlet; these are fed by springs. 4. Those which neither receive running water, nor have an outlet; these are small.

Lakes are also distinguished, according to the quality of their water, into saline and fresh; those which have no outlet, and those situated in a region, whose soil is impregnated with salt, are of the latter class.