FEALE.] TEMPERATURE SOURCE OF HEAT. 383 



hot springs are found on a large scale. Many of the flows are more 

 modern than the rocks of the Park, but in the course of time they 

 have become cooled. It is scarcely to be doubted that the springs at 

 Bear Eiver, in Idaho, were once hot, and one still retains a temperature 

 of 88° r., while others range from 50° F. to 85° F.* It is well known 

 that in the neighborhood of volcanoes that have become extinct, a rapid 

 decrease of temperature may frequently be noted. Between the Aisits of 

 Humboldt and Burkart, a period of 24 years, the temperature of the 

 springs on Jornllo, in Mexico, decreased 40^°. t 



In the Yellowstone National Park, therefore, we must have an enor- 

 mous thickness of trachytes or rhyolitic rocks, if they are simply flows, 

 or the springs must occupy the lines of fissures that exist in bodies of 

 volcanic rock extending to great depths. 



The influence of eruptive or volcanic rocks upon the temperature of 

 water is well shown in the Comstock mines, which are the hottest in the 

 world. Prof. John A. Church, in an article in the American Journal of 

 Sciences and Arts, April, 1879, pp. 288-296, details his observations on 

 the underground temperatures of the Comstock Lode in 1877. He finds 

 that in the lower levels (1,900 to 2,000 feet) there is a pretty uniform 

 temperature of 130° F. The water which filled the Savage and Hale and 

 Norcross mines for two years, gave a temperature of 154° F. In another 

 place it had a temperature of 157° F. Places of exceptionally high 

 temperature were found in narrow belts in the rock. He says, " It is 

 noticeable that the neighborhood of a dike is apt to be hotter than other 

 portions of the rock." 



Prof. J. P. Lesley, in Nature, June 19, 1879 (vol. xx, pp. 168, 169), 

 says that Professor Barker told him that on a visit to the Comstock 

 mines, he found no uniform temperature, but remarkable differences, so 

 that he came to two conclusions — viz: 1st. That the heat was a hot- 

 water heat; and 2d. That the hot waters were heated mechanically by 

 those continuous movements of the country so plainly shown in the 

 mines and at the surface. Professor Lesley asks : 



Has anyone, in the discussion of Mallet's hypothesis, thought of bringing its proba- 

 bility to such a test as the volatilization of the hydrocarbons of coal beds iu a highly 

 plicated region like Belgium ? * * * 



It is a remarkable fact, and one which seems to me inconsistent with the mechanical 

 theory of earth heat, that of two extensive regions, Belgium and Eastern Pennsylvania, 

 equally and excessively disturbed by plications, all of the coal beds of the one are 

 anthracite, and all of the others are bituminous. 



He also compares two undisturbed regions, Western Pennsylvania 

 and Arkansas, which have their coal beds horizontal, and yet one is 

 bituminous and the other anthracite. His idea is that, if movements 

 of the strata produce all the needful heat, no plicated coal beds should 

 escape being converted into anthracite. 



Church, referring to Barker's idea, does not agree with him that the 

 heat is a hot-water heat, nor that it is due to mechanical action. He 

 says :f 



The hot spots are evidently narrow and long, and as the mine openings sometimes 

 intersect and sometimes follow them for some distance, a given level will bo for a 

 part of its length in a hot belt, and for a part in the general mass of heated rock, or 

 one level may be in a hot belt and show a much higher temperature than the level 

 below, which entirely escapes the exceptionally hot ground. 



'Report U. S. Geol. Survey of Terr., for 1878, pp. 594, 595. 



fPhyiscal, Chemical, and Geological Researches on the Internal Heat of the Globe. 

 By Gustavo Bischof, p. 225. 

 { Nature, vol. xx, p. 503. 



