MINERAL MATTERS DISSOLVED. 55 



— 122 0, 9 P.) hold only a small quantity of sulphate 

 of lime in solution. However most springs rising 

 from deep-seated sources contain solid matter, 

 often a great variety of substances, and some one 

 generally in greatest abundance. 



Some persons have entertained most curious 

 notions about the origin of the mineral constituents 

 of springs. The true explanation is, that the 

 water gradually takes up the soluble matters of 

 the strata through which it passes, just as we 

 always see taking place when we put soluble sub- 

 stances into water. Thus the water of by far the 

 greatest number of springs contains some car- 

 bonate of lime (limestone), because lime is one of 

 the most widely spread of all the rocks that form 

 the crust of the earth, and is made slightly soluble 

 by the carbonic acid which is almost always present 

 in the water. Springs which rise out of beds that 

 throw off carbonic acid in considerable quantities, 

 take up a proportionally greater amount of car- 

 bonic acid, and thereby become carbonated waters. 

 If water comes in contact, within the earth, with 

 rocks containing salt, or perhaps even with a bed 

 of rock-salt, it forms a brine more or less saturated. 

 Just in the same manner sulphate of lime, sulphate of 

 soda, iron, magnesia, and sometimes the carbonates 

 of the alkalies, and compounds of sulphur, even sul- 

 phuretted hydrogen, find their way into the spring 

 water. The temperature of the water exerts no in- 



