M. Agassiz on Glaciers, Moraines, and Erratic Blocks. 381 



other causes. Without again recurring to the valleys of drain- 

 age or erosion, I may mention those deep furrows which are 

 not fissures, and which have above them plains of great extent ; 

 also those small lakes which are sometimes formed near the 

 edges of the glaciers, and which so affect the small stones that 

 are accumulated at their margins, as to impress upon them the 

 appearance of stratification ; or again, the analogous phenomena 

 which are observed upon the limits of different stations where 

 the immense sheets of ice have successively stopped in their re- 

 treat ; and likewise the dispersion of the bones of the Mamma- 

 lia at the diluvian epoch, without their being at all rolled or 

 broken, and in short, a number of other particulars which have 

 no interest except when we embrace the whole of the question. 



From this moment the surface of the earth must have been 

 afresh subjected to the influence of the regular succession of 

 the seasons. Then appeared the first spring time of the ani- 

 mals and plants which flourish in our days. The ice had re- 

 tired to the foot of the Alps, and from their summits it began 

 to receive fresh reinforcements. Speedily it reached its last 

 retreats, where it is ever oscillating, sometimes gaining in ex- 

 tent, and forcing the blocks before it, and sometimes again re- 

 tiring within narrower and narrower limits. At each step of 

 ground they abandoned they left behind them, as the existing 

 retreating glaciers now do, some of those long dykes of blocks 

 which still exist in the Alpine valleys. Soon, too, the lakes 

 themselves would melt, the waters would assume their present 

 courses, the valleys of the Alps would be drained, and there 

 remained no more ice, the product of former congelation, ex- 

 cept on the summits of snow-clad mountains. 



It would be a great mistake, therefore, to confound the 

 glaciers which descend from the summits of the Alps with the 

 phenomena of the epoch of that extensive ice which had pre- 

 ceded their existence. 



The phenomena of the dispersion of erratic blocks, then, 

 ought not any longer to be regarded in any other light than as 

 one of the circumstances which have accompanied the vast 

 changes occasioned by the fall of the temperatures of our globe 

 previous to the commencement of our epoch. 



VOL. XXIV. NO. XLVIII. APRIL 1838. C 



