IH Charpentier's Essatj on Glaciers. 



and could have no influence on the form of the sheet of ice ? 

 M. de Charpentier is likewise unable to understand how we 

 are to explain the marks of friction on the rocks by a move- 

 ment of the sheet of ice analogous to that observed in glaciers. 

 In truth this movement in the latter is owing to the congela- 

 tion of absorbed water ; but the congelation of lake or rain- 

 water can only produce ordinary ice, which is neither capable 

 of absorbing water, nor of moving, nor of polishing rocks. 

 The ice of the lakes of the Pyrenees which never thaw, and that 

 of the frozen marshes in the north of Siberia and America, have 

 never assumed the form of glaciers, which appear to exist only 

 by the neve being gradually converted into ice. 



It is from the whole of these considerations taken together, 

 although we can present them only in an abridged form, that 

 M. de Charpentier conceives himself warranted to conclude, 

 that the hypothesis of an extended sheet of ice, is inadequate 

 to explain, in a satisfactory manner, the transportation of the 

 erratic substances of the Alps. 



After having thus passed in review all the theoretical sup- 

 positions hitherto made on the mode of the dispersion of er- 

 ratic blocks, the author comes to that which appears to him 

 the most probable, and to which his observations have contri- 

 buted to give great weight. It is that which ascribes the fact 

 of this dispersion to the action of glaciers, which, if it were 

 once universally adopted, would enable us to define the erratic 

 deposit as a detrltical formatioti deposited bt/ glaciers, while the 

 diluvial w^ould be a detritical formation deposited hy water. 



A rather curious remark of M. de Charpentier's is, that he 

 is not the author of this hypothesis, nor even M. Venets, who 

 was the first, however, that supported the suggestion by direct 

 observations. It appears'that before this time, in 1815, Playfair, 

 in the notes published on his journey among the Alps, regarded 

 the glaciers as the only agent capable of transporting enor- 

 mous blocks to great distances without destroying the sharp- 

 ness of their angles, and that he was not afraid of the extent 

 which, in that case, it was necessary to ascribe to glaciers. 

 The celebrated Goethe also, in the last edition of his IFil- 

 helm Meisfer, published in 1829, advanced the same opi- 

 nion. Lastly, M. de Charpentier mentions the singular fact, 



