Erratics of the xilps. 



303 



spread over the surface of the glacier at the moment of its dissolution, 

 while Jura being the cite of a frontal moraine, would be a landing 

 place for blocks, perhaps for thousands of years. (Charpentier, Essai, 

 p. 267.) Had they been borne on floating-ice the order of distribu- 

 tion would have been reversed ; they would have been most abundant 

 near the source of supply, that is about G k, scarcer at m o, and 

 very scarce on Mount Jura. 



The Steinhoff boulder, containing 61,000 cubic feet, has been 

 mentioned, but there are some others worthy of special notice. One 

 of the most celebrated lies on Mount Jura at x, some hundred feet 

 above Neuchatel (N), and being of easy access, has been visited by 

 crowds of tourists. It is called Pierre a Bot (or toadstone), and 

 measures 50 feet in length, 20 in breadth, and 40 in height. This 

 great block is of granite from the north-east shoulder of Mont Blanc 

 (u), and has been carried to a distance of 80 miles from the parent 

 rock. I was prevented by accident from seeing the Pierre a Bot, 

 but I saw many of the smaller size in the vicinity. 



At Orsieres, near Martigny, there is a granite boulder estimated 

 to contain 100,000 cubic feet, and weighing consequently 8000 

 tons. It is a travelled block, for it rests on a limestone mountain, 

 but it probably has not travelled far. ^xid 



At Monthey (near e) there is a remarkable group of granite 

 blocks, amidst which I spent some hours. They lie on a sort of ter- 

 race, about 400 feet above the bottom of the valley, and form a belt 

 from 300 to 800 feet in breadth, according to M. Charpentier, and 

 a mile and a half in length. One, called Pierre des Marmettes, 

 with a summer-house on its top, is 63 feet long, 32 broad, and 30 

 in height. Another, named Pierre a Mourguets, is 65 feet long. 

 There are many others whose solid contents are from 300 to 400 

 cubic yards. The large ones have their angles almost always sharp, 

 shewing that they have not been rolled or exposed to attrition, and 

 this holds true of the travelled boulders on Jura and in the Alpine 

 valleys generally. All the large blocks at Monthey are of one spe- 

 cies, and belong to the granite of the north-east shoulder of Mont 

 Blanc (near u), from which they are now 27 miles distant. Char- 

 pentier explains their depositation here by a glacier as follows : — 



Fig. 10. 





edi 



1 _____ .^ 070( j fi 



I oi 00d 



h vJlBSa 



sfli 



onox ledgixf 



irrr iud e oafj5 

 __ ^ ^ 



G, Cross section of an ancient glacier occupying the valley (at e, 

 in the map) between the mountains, A B. 



x2 



c d 



__ ; hfX 



I 



* J Li lo 



r. e 



__ 









aodl 



