t"^ Charpentier's Essay on Glaciers. 



species of rocks. M. de Charpentier mentions, among bthers» 

 a band of large blocks near Monthey, in the Valais, from 300 

 to 800 feet broad, and three-fourths of a league long, which is 

 wholly composed of granite with large grains of felspar, de- 

 rived from the mountains bounding the valley of Ferret, 

 eleven leagues distant. Some of them contain 60,000 cubic 

 feet, and they are well preserved. 



We shall not again refer to the singular forms and curiously 

 balanced positions observed in many blocks. With regard to 

 their nature, M. de Charpentier remarks that, if blocks of 

 gneiss and granite seem less common in our days in the plains 

 than on the mountains of Jura, it is partly owing to the fact 

 that, in the former, a great number have been destroyed in 

 order to facilitate cultivation, or to be employed in building, 

 while those, such as conglomerates, which were too hard to be 

 destroyed, have been allowed to remain. In general, the 

 number of blocks is in the inverse ratio of the progress of 

 industry ; and, independently of it being probable that the 

 accumulation was really greater on the sides of the Jm-a than 

 in the plain, it is evident that, in the former position, they 

 have been more secure from the hand of man. 



On the sides of Alpine mountains, the erratic deposit rises 

 to 2200 and 2500 feet above the bottom of the valleys. On 

 the Jura it forms a curve, the upper part of which is on the 

 Chasseron, in front of the great valley of the Rhone, at a 

 height of 3100 feet above the plain, or 4250 feet above the 

 sea ; the extremities of the curve reach the plain, one on the 

 side of Soleure, the other near Gex. This formation is dis- 

 tributed in an irregular manner throughout all the valleys of 

 the basin of the Rhone, also on the sides of the mountains, 

 and over all the plain, from Soleure as far as Mont de Sion, 

 at the western extremity of Switzerland. 



M. de Charpentier then passes in review the various hypo- 

 theses which have been brought forward by different geolo- 

 gists, for the purpose of explaining the mode of transporta- 

 tion of erratic debris. Some (Dolomieu and Ebel) have sup- 

 posed that the Alps at first presented a uniform and inclined 

 plain, on which the blocks have rolled or slided as far the Jura. 

 To this M. de Charpentier replies, that according to the dis- 



