﻿xliv 



PBOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



ceeds 200 fathoms, the increase is only 1° for every 85 feet of 

 depth*. Supposing the increase for greater depths to he at the 

 average rate of 1° for every 100 feet, the temperature of the melting- 

 point of cast-iron, viz. 2786° of Fahr.f, will exist at a depth of 

 somewhat less than 44| miles, that is -^th of the earth's equatorial 

 radius. A cuhic inch of water at 212° expands to nearly a cubic 

 foot of steam, or, more accurately, to 1696 times its volume. By an 

 addition of the pressure of one atmosphere, the mercury standing at 

 30 inches, the boiling-point is raised from 212° to 249° ; and by con- 

 tinuing the heat, without allowing the steam to escape, the boiling- 

 point rises still higher ; and the elasticity of the steam increases with 

 increasing rapidity as the temperature rises. By the experiments 

 of Begnault, it has been shown that by a pressure of 



As the temperature rises by equal additions of heat, the increase of 

 elasticity is more rapid at high than at low temperatures. But it is 

 only when in contact with a body of water from which fresh steam 

 is constantly rising that the elasticity augments in this manner, and 

 thus produces a force sufficient to rend asunder the strongest vessels. 

 If dry steam alone be heated, it follows the law which regulates the 

 expansion and elasticity of gaseous bodies in general J. Thus, in- 

 dependently of the action of water as a constituent of mineral sub- 

 stances, we may, with every degree of probability, consider high- 

 pressure steam to have been the power which rent, shattered, and 

 elevated the sedimentary strata in all geological periods, which 

 drove the softer granites and trappean rocks into rents, and protruded 

 them to the surface, producing the jagged fractures of the upheaved 

 strata — that evident snapping of a hard substance, leaving splintered 

 ends and edges. " In the Alps of Switzerland and Savoy, we find the 

 most stupendous monuments of mechanical violence, by which strata 

 thousands of feet thick have been bent, folded, and overturned, 

 marine secondary formations upheaved to the height of 12,000, and 

 some eocene strata to 10,000 feet above the level of the sea§." To 

 what more probable agency than that of high-pressure steam can Ave 

 ascribe such effects ? 



The powerful part which water has played in the formation of 

 minerals and rocks is shown in a very clear manner by Professor 

 Gustav Bischof of Bonn, in his elaborate ' Lehrbuch der Chemischen 

 und Physikalisehen Geologic,' in four 8vo volumes, the first published 

 in 1847, the last in 1855, showing a vast amount of indomitable 



* Sorbv. Quarterly Journal of Geological Society, vol. xiv. p. 495. 

 t Millers Chemistry, vol. i. p. 194. J lb. vol. i. p. 250. 



§ Ljell, Manual of Geology-, 5th ed., p. 621. 



2 atmospheres, the boiling-point 



is 249-5 



10 

 20 



273-3 

 291-2 

 306-0 

 356-6 

 415-4 



