Geology and Mineralogy. 143 
silica, alumina, ete., in th 
are obtained in the soluble hydrous condition, and therefore they 
at 
the classes of facts already set forth as the concomitants of those 
features,” 
etal P ¢ 
“er aya areas, which are less heavily weighted, forming at once 
. synclinals and anticlinals, If the difference in the densities 
u 
greater, but assumes new phases the Juras and Appala- 
Sane: and finally when the two conditions become extreme, the 
Puen become erup ments are hence accord- 
Tu 
the to hydrostatic law. He says further: “In mountain-making 
disturbing agents have been extreme. All typical mountains 
Sust of granitoid cores protruded through strata and towering 
above them”—as in the Sierra Nevada. “The thickness of the 
