406 SEE— THE CAUSE OF EARTHQUAKES. [October 19, 



secular cooling of the earth, but is all to be explained by the under- 

 mining effect of steam accumulating under the earth's crust. 



17. Mountains in the interior of a dry country, as the Rocky 

 Mountains in Colorado, exhibit no important movements, while 

 those on the coast, like the Andes, are always heaving. This shows 

 that the sea is the cause, and not the secular cooling of the globe, 

 which is wholly insensible. 



18. The only countries which are free from earthquakes are the 

 deserts, and therefore practically uninhabitable ; there is accordingly 

 no escape from earthquakes, and buildings designed for permanency 



.should be framed to withstand them without material injury. 



19. While in the long run the elevation of the land predominates, 

 there is also subsidence, due to the non-concurrence of the forces 

 in certain regions beneath the crust. It is idle to deny these oscilla- 

 tory movements of the crust, and many good illustrations of both 

 are clearly established. Every island which is thrown up in the 

 sea is a witness to one of the most general laws of nature. 



20. As water is taken up in the crust both in the crystallization 

 of rocks and in the processes of earthquake movements, and only a 

 part of this vapor is restored to the surface through volcanic action, 

 there is a secular desiccation of the oceans, but the process is exces- 

 sively slow and not certainly recognizable during the historical 

 period, though a part of the lowering of the strand line in . later 

 geological ages is no doubt traceable to this cause. 



21. The elevation of the plateaus depends on the same cause 

 which upheaved 'the mountains ; and all plateaus, like the mountains, 

 are underlaid with various forms of pumice, which accounts for 

 their feeble attraction as shown by geodetic observations. 



22. No doubt various chemical changes go on under the earth's 

 crust where the water has penetrated the lava and the steam becomes 

 superheated, but the predominance of water vapor in volcanoes 

 shows that the other gases are only by-products, incidental to the 

 moisture and great heat. Dissociation of water vapor is one of these 

 effects. 



23. The details of mountain structure admit of explanation on 

 the present hypothesis, while heretofore no such explanation was 

 forthcoming. A theory which accounts for the position of the 



