M. Renoir on the Traces of Ancient Glaciers. 79 



that descended from the neighbouring summits. It was there- 

 fore as extensive as the bason of the presently existing tribu- 

 taries of the Isere, for the greater part of these tributaries 

 originate from the mountains whose summits are still covered 

 with the remains of these ancient glaciers. Thus, the neigh- 

 bourhood of Grenoble was the receptacle of the ice which de- 

 scended from Mounts Olan and Muande, by the valleys of the 

 Bonne and Drac ; of Veneon or St Christopher ; and the Ro- 

 manche ; and of which the existing remains are the glaciers 

 of Tirbal, Gibernay, and the Grand-Chadou. It was likewise 

 i;he receptacle of the ice which descended from Mount Pel- 

 voux and Mont de P Homme, the remains of which still feed 

 the sources of the Romanche. It also received those accu- 

 mulations of ice, which, by the valleys of the Plainel, Breda, 

 Beins, Azeins, &c. reached the Bocs-du-G rand-Glacier, which 

 they still cover. But even from much greater distances than 

 these were masses of ice conveyed into the bason of Grenoble ; 

 the Boche-Michel and Boche-du-Bonche, near Mount Cenis, 

 still bear the remains of glaciers which descended to that of the 

 Isere by the great valley of the Arc. The portion of the north- 

 east of these deposits, under the name of the glacier oi Grand- 

 Farey, supplies the sources of the Averole, a tributary of the 

 Arc ; and the portion to the south-west or the glacier of Lamet^ 

 is the origin of the Cenise, which discharges itself into the Dora 

 Riparia, one of the tributaries of the Po. Finally, the country 

 around Grenoble had further to receive all the masses of ice 

 which descended from the elevated valleys of Thoron and the 

 Isere, and of which the glacier of Planteri, which feeds the 

 first of these streams, and that of Montets or the Col de la 

 Seigne, which sends the waters produced by its melting into 

 the Isere, and is not above two leagues and a half from Mont 

 Blanc, are remains which, along with those mentioned, and 

 many others besides, indicate the immense power and extent 

 which a glacier formed by the union of so many others, must 

 have possessed in the valley of the Graisivaudan and the lower 

 part of the course of the Isere. 



Between Sapey and the Grande Chartreuse, we likewise meet 

 with small valleys, narrow but deep, surrounded on all 

 sides by very elevated escarpements of large erratic blocks, 

 which no current of water could have transported to the situ. 



