PREVIOUS WORK. 



17 



1873), a portion of which is reproduced in fig. 3, Brooks has failed to 

 outUne the grauitio areas known to the previous explorers. Except in a 



Fig 2.-Enlarged reproduction of a portion of a map of the Lake Superior land district, by Foster and Wlutney. 

 G=granite; T =trappean rocks i d'=iron; t|Bi= beds oi marble. 



Metamorpliio formation. 

 Azoic system. 



Igneo 18 formation. 



(Associated witli the Azoic.) 

 Trappeau rocks. Granite. 



Quartz. Crystalline schists. 



few places, which have been left uncolored, the district is covered with the 

 • color representing the Huroniau. 



MON XXXVI- 



