470 



GEOLOGY. 



Fig. 551 



-Terraces of the Columbia, near Chelan, Wash, 

 gravels. (Atwood.) 



The terraces are of glacial 



Fig. 552. — Glacial lakes in the upper end of a glacial valley (cirque) ; near the head 

 of Commodore Gulch. Silverton, Colo., quadrangle. (R. T. Chamberlin.) 



