SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE— SHERZER. 



PLATE XLII 



I'lG. I.— Development of ice seracs from glacial blocks, Asulkan Glacier, August, i 



904. 



Fig, 



-Disrupted quailzite 1)1 >- :., i.^.^i hca^i ul rar.ulisi. Willey, Canadian Rockies. lUus 

 trating plucking power of glaciers. 



