THE NEW ENGLAND STATES. 11 



controverted by McLaren, 1 Swarz, 2 and others. Swarz does not 

 believe that water from volcanoes and hot springs comes from 

 original magma but is vadose or surface water, and that the heat 

 can be accounted for by assuming sudden pressures or stresses in 

 the earth's crust, the resulting energy being translated into heat. 

 Whether some of our American hot springs and geysers, notably 

 those of the Rocky Mountain region, may not be of surface origin, 

 is for future geological investigation to determine. It seems reason- 

 able to assume, however, in the light of our present knowledge, 

 that the mineral springs in the eastern section of the United States, 

 especially those producing potable waters, and considered in this 

 bulletin, are of vadose origin. 



CHEMICAL AND PHYSICAL AGENCIES AFFECTING COMPOSITION. 



Water being the natural and almost universal solvent, it follows 

 that its mineral characteristic is determined by the character of the 

 rocks and minerals in the earth through or over which the water has 

 passed. Falling in the form of rain or snow, water in the very begin- 

 ning of its cycle absorbs certain gaseous and solid organic and 

 mineral substances. Chemical action resulting in the solution of 

 mineral matter begins as soon as the water starts on its downward 

 course through the earth. The oxygen, carbon dioxid, and organic 

 matter abstracted from the air are extremely active agents in the 

 decompositions subsequently taking place. The oxygen necessary 

 for the oxidation and subsequent solution of certain mineral matter 

 may be afforded entirely, according to Geike, 3 by the volume of this 

 element absorbed by rain water falling through the atmosphere; or 

 there may be a deoxidation and a resulting solution of otherwise 

 refractory mineral matter, the deoxidation being due to the decom- 

 position of organic matter absorbed from the atmosphere or taken 

 into solution by the water while passing through the surface foot or 

 two of soil. One of the products of the decomposition of organic 

 matter is carbon dioxid (CO 2 ), a notably active agent in the decom- 

 position of certain classes of rocks, especially the carbonate rocks of 

 the limestone type. Upon carbonates of calcium and magnesium, 

 carbon dioxid exerts a marked effect. The normal carbonates of 

 these elements are relatively quite insoluble in water free from carbon 

 dioxid. But when carbon dioxid is present these rocks are vigorously 

 attacked and go into solution probably as the bicarbonate of calcium 

 [Ca(HCO 3 ) 2 ] and the bicarbonate of magnesium [Mg(HCO 3 ) 2 ]. Some 

 rocks containing iron are also vigorously acted upon by water charged 

 with carbon dioxid, the iron going into solution as ferrous bicarbonate 



1 Geological Magazine 1906, p. 511. 

 * Geological Magazine 1904, p. 252. 

 a Text Book of Geology, 4th ed., 1903. 



