60 MAN AND THE GLACIAL PERIOD. 



of Switzerland indicate a direction of the ice-movement 

 corresponding to that implied in the distribution of boul- 

 ders. Thus, at K upon the map referred to, Lyell reports 

 that the abundant grooves and strise upon the polished 

 marble all trend down the valley of the Aar.* 



Similar facts concerning the transportation of boul- 

 ders have been observed at Trogen, in Appenzel, where 

 boulders derived from Trons, one hundred miles distant, 

 are found to keep upon the left bank of the Rhine, how- 

 ever much the valley may wind about ; and in some places, 

 as at Mayenf eld, it turns almost at right angles, as did the 

 Rhone at Martigny. Upon reaching the lower country at 

 Lake Constance, these granite blocks from the left side of 

 the valley deploy out upon the same side and do not cross 

 over, as they would inevitably have done had they been 

 borne along by currents of water. 



In America Ave do not have quite so easy a field as is 

 presented in Switzerland for the discovery of crucial in- 

 stances showing that boulders have been transported by 

 glacial ice rather than by floating ice, for in Switzerland 

 the glaciated area is comparatively small and the diminu- 

 tive remnants of former glaciers are still in existence, fur- 

 nishing a comprehensive object-lesson of great interest 

 and convincing power. Still, it is not difficult to find 

 decisive instances of glacial transportation even in the 

 broad fields of America which now retain no living rem- 

 nants of the great continental ice-sheet. 



As every one who resides in or who visits New England 

 knows, boulders are scattered freely over all parts of that 

 region, but for a long time the theory suggested to ac- 

 count for their distribution was that of floating ice during 

 a period of submergence. One of the most convincing 

 evidences that the boulders were distributed by glacial ice 

 rather than by icebergs is found in Professor C. H. Hitch- 



* Antiquity of Man, p. 305. 



