80 M. Renoir on the Traces of Ancient Glaciers. 



ations tliey occupy ; for, according to the divers characters of 

 the rocks forming these blocks, it would have been necessary 

 that the current should have been capable of conveying some 

 of them, without allowing them to touch the earth, from the 

 first chain which extends in the direction of Vizille to Al- 

 levard, to beyond the calcareous mountains of Chartreuse, a 

 medium distance of five leagues ; others of them, from the 

 chain which separates the department of the Isere from that 

 of the High Alps and La Maurienne, by causing them to pass 

 over the first and supporting them at this great height during 

 their passage, which, at the shortest, could not be less than 

 six leagues, while, in many cases, it would amount to twelve. 

 Finally, others, belonging from their nature to the central 

 chain of this part of the Alps, I mean the chain which passes 

 Mont Blanc to the east of Brian9on, would necessarily have 

 to be transported, at the least, over a space of fifteen leagues, 

 and the greater number over a space from twenty-two to 

 twenty-six leagues ; and that too, while being constantly sup- 

 ported at an absolute medium height of about 3000 metres, 

 and about 2700 metres above the town of Grenoble, for they 

 would have to be carried over the two chains of which we 

 have spoken. It is to be observed that the medium height of 

 the second of these being sensibly the same as that of the cen- 

 tral chain, these enormous masses of blocks could not even 

 deviate in the smallest degree from their course, without be- 

 ing arrested by the second chain and precipitated into the 

 Alpine valleys. 



If we suppose that the erratic blocks have come from other 

 parts of the Alps, the difticulties of height will be still the 

 same, and even more numerous, and the passage longer. 



Lastly, We may here repeat the fact, which is in such ob- 

 vious contradiction to the system of transportation of erratic 

 blocks by great currents, namely, that these blocks and large 

 rolled pebbles are scattered, in a fan-shaped form, not only 

 around the Alps, but also around all the other systems of 

 mountains where they have been observed ; so that all these 

 mighty currents must have originated from the very summit 

 of each chain, and radiated in every direction ; which is alto- 

 gether incomprehensible. Besides, according to the commu- 

 nications we have received from recent scientific travels, this 



