i8 



boulder conglomerate rests nearly horizontally. This has the 

 characters of tillite, a matrix of graywacke enclosing angu- 

 lar, sub-angular and rounded stones of all sizes up to boul- 

 ders several feet in diameter. Among these stones are many 

 of quartzite and granite, the nearest outcrop of the latter 

 rock occurring five miles to the southeast. No striated 

 stones have yet been found in the tillite, perhaps because it 

 is almost impossible to separate the stones from the matrix. 

 Dr. Collins has traced this conglomerate northeast with 





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i 1 "#m 3 \ 









Structure in Gabbro, Sudbury. 



scarcely a break to the basal conglomerate at Cobalt ; and 

 the present writer has followed it, with some intervals, to 

 the lower Huronian conglomerate of the typical Huronian 

 region toward the west. 



The conglomerate, like the lower rocks, is often crushed 

 into a breccia composed of large blocks cemented by more 

 finely ground materials. This took place during the dis- 

 turbances caused by the advent of the nickel eruptive. The 

 tillite or conglomerate is the only lower Huronian rock 

 found, and the middle Huronian is entirely absent. 



