278 THE ICE AGE IN NORTH AMERICA. 



Parallel." Speaking of the streams which rise in the Rocky 

 Mountains, he says : 



The upper ends of the valleys surrounding the higher peaks 

 and ridges are generally very abrupt and take the form of 

 cirques, or amphi theatrical depressions of great depth, in the 

 mountain - sides. The backs and sides of these are often 

 nearly vertical, and they are sometimes only separated later- 

 ally, by steep, knife-edge-like ridges, the crests of which form 

 the most practicable paths to the summits. Each of these 

 upper terminations of the valleys generally also shows a small 

 lake or pond in the hollow of the surrounding cliffs, the basin 

 of which has evidently been formed by glacier-ice — which must 

 here have been descending almost vertically — in the moraine 

 matter or shattered rocky floor. . . . The water of the smaller 

 lakes in the upper ends of the valleys, as seen from the heights 

 around, is of a beautiful semi-opalescent indigo-blue, and must 

 be of considerable depth.* 



These facts confirm the theories of the leading glacialists 

 of Europe — for instance, Dr. Albrecht Penck, who ascribes 

 the excavations of the most important lake-basins in Bavaria, 

 like the Ammer See and Wurni See, to glaciers, and states 

 that u a lake-basin filled with water or sediment lies at the 

 mouth of each of the Alpine valleys through which glaciers 

 protruded in ancient times." f 



The Scotch lochs, and the rock-basins of Norway, would 

 seem to be due to the same cause. It is probable also that 

 f .he fiords of Norway and of British Columbia owe their 

 greater depth near their heads to the same anomalous influ- 

 ence of ice-erosion. Most of the arguments urged against 

 the theory are based upon a priori reasons urging the impos- 

 sibility of any such result from such a cause. Of this more 

 will be said when speaking a little later of the irregular depo- 

 sition of glacial debris underneath the moving ice. 



Not enough is known about the nature of ice to affirm 





* Page 245. 



f Quoted by Newberry, in " School of Mines Quarterly," January, 1885, p. 10. 



