114 WALKS AND TALKS. 



shook the ground and bulged the terrestrial crust into mount- 

 ain saliences. They had seen mountain caps blown off, and 

 mountains cracked open"; they had even seen Sabriiia and 

 Graham's Island and many ^Egsean islands lifted from the 

 bottom of the sea, and sustained at an elevation of some hun- 

 dreds of feet. Were not these efforts at mountain-making and 

 unmaking? Had it not been ascertained, too, in more recent 

 times, that Vesuvius and jiEtna, with all their loftiness and 

 massiveness are mere piles of stuff brought up by volcanoes, 

 and builtj by volcanic action into mountain forms ? Is not 

 Mt. Hood a pile of lava? And who can affirm that Ranier, 

 Lassen, St. Elias, Popocatapetl, Cotopaxi, are not similarly 

 masses of piled up lavas? 



Yes, the reasoning is good for a certain class of mountains. 

 But the Adirondacks are not a pile of lava ; nor the Lauren- 

 tides; nor the Appalachian ranges; nor the White Mount- 

 ains; nor the Rockies. Here has been lifting to which 

 all volcanic work bears a very feeble comparison. If 

 .^Etna and Hood are piles of volcanic debris, consider how 

 small a part was lifted at once. The ascent of the mount- 

 ain materials has been like that of wheat in the grain 

 elevator little at a time, but much in the aggregate. 

 Look at the Adirondacks, on the other hand here is a vast 

 framework; all the parts were formed and adjusted together 

 before the uplift; and when the time arrived, the total mass 

 was raised in one stupendous mechanical effort. We must 

 seek a greater power than the volcano. 



It is not a trivial problem. It has puzzled the most ex- 

 pert of brains. But I think you have made the acquaintance 

 of forces and modes of action which furnish us a real clew to 

 the mechanism of mountain making. Your attention has been 

 directed to many indications of the presence and action of 

 heat in the earth. You have even reached the inference that 

 the earth is a cooling globe. [But see further in Talks 

 XXXVII and XXXVIII.] Now, you have often witnessed 

 the power of heat. When it enters a solid or liquid, expan- 

 sion takes place, and the power of expansion surpasses human 



