THE CONTINENTAL GLACIERS OF THE "ICE AGE" 305 



regions. A relic of Buckland's earlier view we have in the word 

 " diluvium " still occasionally used in Germany for glacier trans- 

 ported materials ; while the term " drift " still remains in common 

 use to recall Lyell's iceberg hypothesis, even though the original 

 meaning of the term has been abandoned. Drift is now a generic 

 term and refers to all deposits directly or indirectly referable to the 

 continental glaciers. 



In general the place of derivation of the glacial drift may be said 

 to be some point more distant from and within the former ice mar- 

 gin at the time 



when it was de- x$id$ 



posited ; in other 

 words, the dis- 

 persion of the 

 drift was cen- 

 trifugal with ref- 

 erence to the 

 glacier. 



Wherever 

 rocks of unusual 

 and therefore 

 easily recogniz- 

 able character 

 can be shown to 

 occur in place 

 and with but lim- 

 ited areas, the 

 dispersion of 

 such material is 

 easy to trace. 



The areas of red Swedish and Scotch granite have been used to 

 follow out in a broad way the dispersion of drift over northern 

 Europe. Within the region of the Great Lakes of North America 

 are areas of limited size which are occupied by well marked rock 

 types, so that the journeyings of their fragments with the conti- 

 nental glacier can be mapped with some care. Upon the northern 

 shore of Georgian Bay occurs the beautiful jasper conglomerate, 

 whose bright red pebbles in their white quartz field attract such 

 general notice. At Ishpeming in the northern peninsula of Michi- 



i s \ 



FIG. 331. Map to show the outcroppings of peculiar rock 

 types in the region of the Great Lakes, and some of the 

 localities where "float copper" has been collected (float 

 copper localities after Salisbury) . 



