EVIDENCE OF FOSSIL REMAINS 85 



crystalline or plutonic rocks like the original mass of 

 the earth and the kinds forced to the surface by vol- 

 canic eruptions. Later the earth wrinkled again in 

 various ways and places so that new ridges and moun- 

 tains were formed with new systems of lakes and oceans 

 and rivers ; and again the elements continued to erode 

 and partially destroy the higher masses and to lay down 

 new and later series of sedimentary rocks upon the old. 

 It seems scarcely credible that the apparently weak 

 forces of nature like those we have mentioned are suffi- 

 ciently powerful to work over the massive crust of the 

 earth as geology says they have. Our attention is 

 caught, as a rule, only by the greater things, like the 

 earthquakes at San Francisco and Valparaiso, and the 

 tidal waves and cyclones of the South Seas ; but the re- 

 sults of these sporadic and local cataclysms are far less 

 than the effects of the persistent everyday forces of 

 erosion, each one of which seems so small and futile. 

 When we look at the Rocky Mountains with their high 

 and rugged peaks, it seems almost impossible that rain 

 and frost and snow could ever break them up and wear 

 them down so that they would become like the rounded 

 hills of the Appalachian Mountain chain, yet this is 

 what will happen unless nature's ways suddenly change 

 to something which they are not now. A visitor to the 

 Grand Canon of the Colorado sees a magnificent chasm 

 over a mile in depth and two hundred miles long which 

 has actually been carved through layer after layer of 

 solid rock by the rushing torrents of the river. Per- 

 haps it is easier to estimate the geological effects of a 

 river in such a case as Niagara. Here we find a deep 

 gorge below the famous falls, which runs for twenty 



