Page:A Treatise on Geology, volume 2.djvu/271

 CHAP. IX.

To complete this view of the chemical characters of hot springs, we may notice some of those which rise in volcanic countries.

None of the facts disclosed by chemical analysis of these springs, justify the belief that it is to any peculiar chemical action in their channels that their heat above the atmosphere is owing. On the contrary, their heat is derived by communication from the heated rocks through which they pass, whatever may be the cause of their chemical differences. (See professor Forbes's remarks, Phil. Trans. 1836, p. 576.) That the heat of the rocks, and therefore that of the springs, is derived from volcanic action, appears to Dr. Daubeny probable, because nitrogen gas, so commonly evolved from hot springs, is also a product of volcanos, both subaerial and submarine, and because "the majority of thermal waters arise, either from rocks of a volcanic nature, from the vicinity of some uplifted chain of