SIGNS OF PAST GLAGIATION. 59 



is at work transporting boulders and moraines according 

 to the law of ice-movement. Following down the valley 

 from A, boulders from the head of the Rhone Valley are 

 found distributed as far as B at Martigny, where the val- 

 ley turns at right angles towards the north. It is evident 

 that floating ice in a stream of water would by its momen- 

 tum be carried to the left bank, so that if icebergs were 

 the medium of transportation we should expect to find 

 the boulders from the right-hand side of the Rhone Val- 

 ley distributed towards the left end of the great valley of 

 Switzerland — that is, in the direction of Geneva. But, 

 instead, the boulders derived from C, D, and E, on the 

 Bernese Oberland side, instead of crossing the valley at 

 B, continue to keep on the right-hand side and are dis- 

 tributed over the main valley in the direction of the river 

 Aar. 



As is to be expected also, the direct northward motion 

 of the ice from B is stronger than the lateral movement to 

 the right and left after it emerges from the mouth of the 

 Rhone Valley, at F, and consequently it has pushed for- 

 wards in a straight line, so as to raise the Alpine boulders 

 to a greater height upon the Jura Mountains at G than 

 anywhere else, the upper limit of boulders at G being 

 1,500 feet higher than the limits at I or K on the left and 

 right, points distant about one hundred miles from each 

 other. All the boulders to the right of the line from B to 

 G have been derived from the right side of the Rhone, 

 while all the boulders to the left of that line have been 

 derived from its left side. 



A boulder of talcose granite containing 61,000 French 

 cubic feet, measuring about forty feet in one direction, 

 came, according to Charpentier, from the point n, near 

 the head of the Rhone Valley, and must have travelled 

 one hundred and fifty miles to reach its present position. 



It scarcely needs to be added that the grooves and 

 scratches upon the rocks over the floor of this great valley 



