i\I. Cliarpentier oa the Erratic Phcmmcna of the North. 69 



from north to south ought to have" {Mem. p. 17.) I quote 

 this fact, because it explains extremely well the crossing of 

 the striae Avhich is sometimes remarked on the surface of rocks. 

 The localities where the stria? cross have been covered at two 

 different times by ice ; the first time, they have been invaded 

 by the great glacier, which has scratched them in the general 

 direction from north to south ; and the second time, they have 

 been so by partial glaciers, whose action has there produced 

 striae, in some degree anomalous, which cross the first in va- 

 rious directions. 



When two of these partial glaciers became joined together 

 and united into a single one, they would give rise to a super- 

 ficial moraine. {Essai, § 20 and § 21.)* 



The abraded and polished surfaces of rocks, the stria?, fur- 

 rows, and caldron-like erosions, could only be produced dur- 

 ing the period when the various localities where they are ob- 

 served were covered by ice. The direction of the furrows and 

 striaj being generally from north to south,, we are authorized 

 in believing that the principal movement of the glacier was in 

 that direction. 



In order to assign the cause v/liiuh determined this direc- 

 tion, we must turn our attention to the state of the snow in 

 the north during the epoch of which we are speaking. I have 

 already remarked that the whole erratic phenomenon obliges us 

 to admit that some time after the last great catastrophe which 

 altered the configuration of the northern hemisphere, the cli- 

 mate became so much colder, that in Scandinavia, perhaps 

 from the 60th degree, the summer heat Mas no longer suffi- 

 cient to cause the complete melting of the winter snows. Ne- 

 vertheless, the liquefaction was not entirely suspended, and the 

 water proceeding from it, as well as that derived fi'om rain, 

 must gradually have converted the snow into a glacier which 

 invaded countries more to the south and having a milder cli- 



* The bsars which have had this origin may be recognised by the fact 

 that their upper extremity generally rests against the rock or eminence form- 

 ing the termination of the chain of mountains, which, by separating the two 

 glaciers, has given rise to the deposit of the superficial moraine (Essai. p. 55 

 fig. xii., c and 1.) This appearance has been supposed to be an evident proof 

 of the formation of osars by a powerful current. 



