American Association. 257 



zose conglomerates, in avMcIi blood-red jasper pebbles become 

 largely mingled with tliose of white quartz, and in great mountain 

 masses predominate over them. But the series is here much 

 intersected and interstratified with greenstone trap, which was not 

 observed on lake Temiscaming. 



These rocks were traced along the north shore of Lake Huron, 

 from the vicinity of Sault Ste. Marie for 120 miles, and Mr. Mur- 

 ray ascertained that their limit on the Lake Shore occurred near 

 Shibahahnahning, where they were succeeded by the underlying 

 group. The position in which the group was met with on Lake 

 Temiscaming is 130 miles to the north east of Shibahahnahning, 

 and last year Mr. Murray, in exploring the White Fish River, was 

 enabled to trace the out-crop of the group characterized by slates, 

 sandstones, conglomerates, greenstones, and copper-lodes for sixty 

 five miles from Shibahahnahning to the junction of the Maskinonge 

 and Sturgeon rivers, tributary to Lake Nipissing. The general 

 bearing of the out-crop is N". E,, and an equal additional distance 

 in the same direction, would strike the exposure on Lake Temis- 

 caming. In the portion which Mr. Murray examined last year, the 

 dip appears to be about N". "W., often at a high angle, while that 

 of the subjacent gneiss is more generally S. E., sometimes at a low 

 angle, and in some places nearly horizontal. To the eastward of 

 this out-crop, Canada has an area of 200,000 square miles ; this 

 has yet been but imperfectly examined, but in so far as inves- 

 tigation has proceeded, no similar series of rocks has been met with 

 in it ; and it may safely be asserted that none exists between the 

 basset of the Lower Silurian and the gneiss^ from Shibahahnahning 

 to the Mingan Islands, a distance of more thanl,000 miles, and 

 probably still farther to Labrador. The group on Lake Huron we 

 have computed to be about 10,000 feet thick, and fi-om its volume, 

 its distinct lithological character, its clearly marked date, posterior 

 to the gneiss, and its economic importance as a copper-bearing 

 formation, it appears to me to require a distinct appellation and a 

 separate color on the map ; without which, indeed, the investigation 

 of Canadian geology could not be conveniently carried on. We 

 have in consequence given to the series the title of Huronian. A 

 distinctive name being given to this portion of the Azoic rocks 

 renders it necessary to apply one to the remaining portion. The 

 only local one that would be appropriate in Canada, is that derived 

 from the Laurentide range of mountains, which is composed of it 

 from Lake Huron to Labrador. We have therefore, designated it 



