G8 M. Charpentier on fJ/e Erratic Phenomena of the Nurih. 



themselves are not uninterruptedly skirted by moraines; f.r 

 the latter cannot be met with except in the localities where 

 the rocky debris have reached the edge of the glacier, and 

 where torrents have not prevented its accumulation. Moreover, 

 in places where the glacier deposited little matter, the moraine 

 having remained small and but little elevated, has been after- 

 wards buried by the diluvium, and thus removed from the 

 view of the observer. 



On each occasion when the glacier, during the process of 

 melting, was subjected to some oscillation, it gave rise to 

 new accumulations of debris. In this manner it necessarily 

 formed other frontal moraines ; these are recognised by their 

 direction, which is nearly east and west, and they are known 

 in eastern Prussia by the name of Steuiduniviie. 



Having at last retreated beyond the Baltic, the glacier was 

 so much reduced as only to occupy the regions in which it had 

 originated. The return of a milder climate must also have 

 gradually produced a melting in these countries. We can 

 easily conceive that the lower regions were the first that were 

 freed from ice ; but that the latter kept its ground on the moun- 

 tains and higher table-lands, until the return of heat had also 

 reached such elevated points. Previous to this complete melt- 

 ing, the glacier was, so to speak, lacerated or divided into 

 shreds, forming so many separate glaciers, of v/hich the largest, 

 as happens in the Alps, descended into the neighbouring val- 

 leys, and, depositing on the flanks of the mountains the debris 

 which they transported, caused the formation of the Scandi- 

 navian ijsars of the present day. When the mountain which 

 retained its ice, was more or less isolated, or advanced into the 

 fiat country, so that the glacier which descended fi'om it could 

 extend freely over a smooth surface, there would result the 

 jdienomenon desci'ibed by M. Durocher, and which consists in 

 this, " that in taking each of the rocks which have furnished 

 erratic blocks as the centre of a circle, the region which con- 

 tains blocks derived from that rock, occupies more than a third, 

 and sometimes nearly a half, of the circumference, so that the 

 blocks have followed, in certain ca.ses, a line almost perpen- 

 dicular to the general direction which tlie power of transport 



