X 



THE GEOLOGIST. 



in its coarsest form, near the extremities of certain glaciers, 

 he concludes they were once the moraines of glaciers which 

 melted away and retired from them. He then goes on to 

 suppose that when the recession of the glaciers took place, 

 (an effect which he refers to the same cause as De Saussure), 

 such transversal moraines formed dykes standing out at 

 some distance from the mountain, and barred up lakes 

 formed by the melting of the ice and snow. These lakes, 

 at length swollen to excess, are supposed to have burst 

 through the moraine barrier, and to have drifted the materials 

 of which it was composed, into the lower countries. To the 

 same cause he attributes the presence of large boulder stones 

 in the Alps, and he concludes that no such boulder stones 

 are to be found in any localities where there are not per- 

 manent glaciers. 



This opinion which we have drawn, from the peru- 

 sal of the author's work, is refuted in the address of 

 the President of the Geological Society of London, by 

 reference being made to the extensive distribution of 

 erratic blocks in the large valley of the north of Germany ; 

 nor does he, as Mr. Murchison says, explain how it has 

 happened that the granite blocks of Mount Blanc should lie 

 upon the Jura. 



In fact, the force required to effect changes of that extent 

 as are now visible on the surface of certain districts, must 

 have been much greater that any which could arise from 

 glacial progresses alone. Whilst, when water is added to 

 the agency, power and volume are both gained — both of 

 them essential attributes of any agent. 



Mr. Godefroy argues much in the same way. He con- 

 siders the ancient diluvial deposit as formed in the manner 

 detailed by ^l. Necker de Saussure, and that the so-called 

 moraines are only re- arranged j)ortions of some pre-existing 

 diluvial deposit, placed in their present i:)osition by the 



