STATE GEOLOGIST. 51 



stone containing fossils in a perfect state of preservation. A 

 conglomerate also occurs here, made up of rounded masses of 

 quartz, ranging from the size of a pea to boulders many tons 

 in weight, all cemented together by a silicious limestone, not 

 altered, but appearing as if deposited amongst the interstices 

 and open spaces of a pile of stones and gravel. 



The solid quartzose character of the rock on St. Joseph's and 

 Sulphur Islands, so unlike the conglomerate and altered sand- 

 stone of Lake Superior, seems to suggest the idea of its 

 being azoic, and it is so colored on Poster and Whitney's 

 map, where, nevertheless, it is made to appear like a prolonga- 

 tion of the Potsdam sandstone of Sugar Island. The gradual 

 transition, however, from the unaltered sandstone of the Sault, 

 to the altered sandstone of Neebish Eapids and the extrem- 

 ity of St. Joseph's Island, the quartzose sandstone and jas- 

 pery conglomerate of the shore west of Campement d'Ours, 

 and the quartz and conglomerate of Sulphur Island, fa- 

 vors the idea of the equivalency of the sandstone and quartz- 

 ose rocks. The superposition of fossiliferous limestone, at 

 Sulphur Island (probably the Chazy limestone) immediately 

 upon the quartzite, favors the same inference, inasmuch as 

 there is no probabiilty that the sandstone would not be inter- 

 posed at this place between the Chazy and the azoic rocks. 

 Moreover, the influence of the igneous disturbances which 

 have taken place at the Bruce mines and along the Canadian 

 shore but a few miles distant, furnish sufficient cause for the 

 alteration suggested. The Canadian geologists have frequently 

 recognized the Potsdam sandstone in a similar 'condition. 



2. — Galciferous Sandstone. 



Though this formation, as just stated, is not recognized to 

 the east and south of St. Mary's Falls, it is thought best to em- 

 brace it in the enumeration, since it is represented as playing 

 an important part in the geology of the country west of St. 

 Mary's river. 



