478 REPOKT OF NATIONAL MUSEUM, 1899, 



AcH'ordini,^ to their temperatures as they flow from the .spriiig-s the 

 waters are divided primarily into (A) thermal and (B) nonthermal, a 

 thermal water being- one the mean annual temperature of which is 

 70° F. or above. Eaeli of these groups is agam subdivided according 

 to the character of the acids and their salts held in solution as below: 



Class I. Alkaline. 



Class II. Alkaline-saline-j^f'^^naS' 



Class III. Saline {Muriated. ' 



ISulphated. 

 Muriated. 

 ^.,. . rSulphated. 



^il^"0"^--iMuriated. 



Any spring of water may be characterized by the presence or 

 absence of gas when it is designated by one of the following terms: 

 (1) Nongaseous (free from gas). (2) Carbonated (containing carbonic- 

 acid gas). (3) Sulphureted (containing hydrogen sulphide). (4) Azo- 

 tized (containing nitrogen gas). (5) Carbureted (having carbureted 

 hydrogen). 



In cases where there is a combination of gases such is indicated by a 

 combination of terms, as sulphocarbonated, etc. The classes may be 

 further subdivided according to the predominating salt in solution, as 

 (1) sodic, (2) lithic, (3) potassic,(4) calcic, (5) magnesic, (6) chalybeate, 

 (7) aluminous. 



The alkaline waters, Class I above, include those which are charac- 

 terized by the presence of alkaline carbonates. Generally such are 

 characterized also by the presence of free carbonic acid. Nearly one- 

 half the alkaline springs of the United States are calcic-alkaline, that 

 is, carry calcium carbonate as the principal constituent. The saline 

 waters include those in which sulphates or chlorides predominate. 

 They are more numerous than are the alkaline waters. The alkali-saline 

 class includes all waters in which there is a combination of alkaline 

 carbonates with sulphates and chlorides; the acid class includes all 

 those containing free acid, which is mainly carbonic, though it may be 

 silicic, muriatic, or sulphuric. 



The character of the salts held in solution is the same for both ther- 

 mal and nonthermal springs, though as a general rule the amount of 

 salt is greatest in those which are classed as thermal. Thus at the Hot 

 Springs of Virginia one of the springs, with a temperature of 78° F., 

 has 18.01) grains to the gallon of solid contents, while another, with a 

 temperature of 110° F., has 33.36 grains to the gallon. 



Source of mineral tvaters. — Pure water is a universal solvent and its 

 natural solvent power is increased through the carbonic acid which it 

 takes up in its passage through the atmosphere, and by this same acid 

 and other organic and inorganic acids and the alkalies which it acquires 

 in passing through the soil and rocks. The water of all springs is 



