GLACIAL SUCCESSION IX CENTRAL LUXENBURG PREST. 167 



of northern, origin. This shows that the ice sheet did not recede 

 far enough to gather before it in its second advance any northern 

 drift, while the slight oxidizing of the lower beds reveals a 

 length of time which is very limited when compared with that 

 of the first great interglacial epoch. This epoch is often repre- 

 sented by a slight denudation of the oxidized part of the under- 

 lying boulder clay. 



Third Glacial Epoch. 



This, the last invasion of this district by the ice sheet, has 

 left as its legacy the local auriferous drift of Blockhouse and 

 Dorey's Brook. In both these places it was probably gathered 

 from exposed hummocks and loose debris in the immediate 

 neighbourhood. It consists largely of angular slate boulders 

 and oxidized clay and gravel, with here and there a few boulders 

 eroded from the lower till. The most noteworthy point in this 

 deposit, aside from the fact that it contains the gold-bearing drift 

 of Blockhouse, is that the direction of its movement is different 

 from that of the lower boulder clay. While the course of the 

 latter has been about S. 22 E, that of the former has been from 

 S. 50 to 55 E. Thus, while the underlying drift has been 

 subject to continental or at least provincial influences, the upper 

 drift is local both in composition and course of movement. At 

 Dorey's Brook, also, the course travelled by the upper drift is 

 influenced by the local surface contour. Its course is about 

 S. 65 E., while that of the quartz in the interglacial clays is 

 N. 80 to 90 E., and the underlying boulder clay probably 

 S. 40 E. The tracing of the course travelled by the different 

 layers of drift, is often a painstaking and difficult study, where 

 no striations are left as a guide. But once its origin and the 

 course it has travelled are known, it becomes our most reliable 

 guide in the search for gold-bearing veins, and as such will 

 repay the most patient investigation. 



Post Glacial Epoch. 



The deposits of this epoch consist of modified drift and river 

 terraces. At this time the land appears to have been more 

 elevated than at present, during which the beds of many of our 



