Theories of the Formation of Mountains. 415 



again distinct from the last upheaval which brought up the whole 

 region above the level of the sea, laying dry the horizontal New 

 Red Sandstone, as well as a great part of, if not all, the Appala" 

 chian chain." {LyelVs Travels in North America^ \st Visit 

 Vol. 1, p. 78.) 



Theory of the Contraction of the Sphere of the Earth. 



This theory supposes that the earth was originally a fluid mass 

 of great dimensions — that in cooling down it contracted, and that 

 the plications of mountain chains have been produced by the 

 folding of the crust consequent on contraction. This theory 

 originated with Leibnitz and has been adopted by very many of 

 the great physicists who have lived since his day. In America it 

 has been investigated by Professor Dana and applied to the solu- 

 tion of tbe problem of the plication of the Appalachians. (See 

 SilHman's Journal, 2 series. Vol. 2,pageZ%b,and Vol, Zjpage^^:. 



Buffon's Theory, 



Buflfon was of opinion that mountains and mountain chains are 

 of submarine origin or that they are simply huge petrified mud 

 or sand banks originally accumulated on the bottom of the sea, 

 by the action of the waves and currents, and afterwards elevated, 

 along with the continents by subterranean forces. Buffon, it is 

 scarcely necessary to state, never applied this idea to the Appa- 

 lachians, but as it forms part of Professor Hall's theory, we quote 

 it here; we have published it in the 1st Volume of this Journal, 

 page 8. 



Sir John Herschel's Theory. 



Sir John Herschel is of opinion that the sediment as it accumn- 

 iates on the bottom of the Ocean must by its weight cause the 

 earth's crust immediately beneath to sink, while the fluid matters 

 below being thrust aside and forced under the adjacent parts ele- 

 vates tracts of land where there is no such accumulation in pro- 

 gress. In consequence of the swelling up of the surface in those 

 rising regions, the strata are sometimes strained beyond their 

 power of cohesion and cracked asunder, and thus fissures are pro- 

 duced through which the molten rock of the interior boils out 

 upon the surface. Thus volcanoes, great overflows of trap, and 

 mountains may have originated. The fact that nearly all volca- 

 aoes are found near the sea shore or near the margins of those 



