156 l. «. RUSSEL1 CTRPACE GEOLOGY OF ALASKA. 



doctrine of a northern elevation as a cause of glaciation seems to be excluded 

 by present disclosures. It Beema t" me that by the above line of observa- 

 tion we have almost excluded extra-terrestrial causes, and by the demon- 

 stration of the lower altitude of the surface we have excluded those causes 

 that were relied upon by Lyell and others in the earlier days. Ii Beems to 

 tin-, further, that it is impossible t<> account for the glacial period by any 

 Bupposable change in precipitation. We have, in the north Pacific regioni 

 :it the present time, the most extraordinary precipitation, and yet we find 

 that these Ala.-kan mountains are not the centers from which extensive ltIu- 

 ciation radiates. I therefore find very grave difficulties in connecting the 

 former glaciation with any climatological change that can be supposed to 

 have taken place with the earth's axis of rotation where it now is. 



