M. Renoir on the Traces of Ancient Glaciers. 77 



peculiar structure of birch-wood, which is always so soft in our 

 moors which have not been dried up, that it can be easily 

 crumbled together between the fingers, while oak and fir are 

 by no means so much softened. So small a pressure as that 

 exercised by 8 or 10 feet of drift-sand is quite sufficient to 

 flatten birch branches. 



EXPLANATION OF THE FIGURES IN PLATE III. 

 Fig. 1. near the village of Skiveren ; a, horizontally stratified beach sand; 

 6, bed or vein of beach stones : c, drift sand. Fig. 2. interrupted and 

 saddle-shaped arrangemcAts of the eand. Fig. 3. between Lyngbye 

 and Lbkken : aa, blue clay ; hh, Martorv ; c, earth ; dd, drift sand ; «, 

 cut made by the rivulet. Fig. 4. between Skiveren and Hoien ; a, beach 

 sand with rolled stones ; h, beach sand covered with the stone bed ex- 

 posed by the wind 'y ccc, Martorv ; dd, drift sand ; ee, portions of the 

 Martdry which have fallen down : /, the beach ; ^, the sea. 



On the Traces of Ancient Glaciers which have filled the Valleys 



of the Alps of Dauphiny, and on those of the same nature^ 



7vhich appear to result from some of the Observations made 



by M. Bobert in Northern Russia, By M. Renoir. 



Having traversed the Grand-Chartreuse alone, a few days 



before the meeting of the Society at Grenoble, I thought it 



unnecessary to go over the same ground again a few days 



afterwards. 



In the minutes which were read after the return of the So- 

 ciety, it was stated that rocks polished by erratic blocks had 

 been observed at Fontenil. As I had not visited that locality, 

 in consequence of having returned by coach, I could make no 

 objection to this statement in the minutes, but I resolved to 

 visit the rocks in question. 



The day after the breaking up of the Society, therefore, 

 M. Gras and I repaired to the quarries of Fontenil. We had 

 the satisfaction of finding there many polished surfaces, as 

 beautiful and as well preserved as any that can be seen among 

 the Swiss Alps or on the southern declivity of the Jura. But 

 the appearance of the furrows with rounded edges, and par- 

 ticularly the system of fine striiP, very parallel and all running 

 in the general direction of the valley of the Isere, shewed us 

 that the surfaces had not been polished by blocks, but rather, 

 like those of the regions mentioned, by an immense glacier 

 which has at some remote period moved throughout the whole 



