LOWER SILURIAN OF CAPE BRETON — GILPIN. 169 



at the mouth of Sahiion River, where these measures are inter- 

 posed between Lower Carboniferous limestone and Laurentian 

 felsites. The felsite rocks cut out this patch and ahnost com- 

 pletely surround it. Still passing toward the head of the lake, 

 after an interval of about a mile, the Silurian strata are met 

 again, and occupy the shore of the lake to its head, and the banks 

 of the Giant Lake River to the foot of Giant Lake. This ex- 

 posure, about seven miles long and four wide, projects into the 

 felsites of the Mira Hills, and is in several places pierced by 

 masses of felsite. 



The shore of the lower half of Giant Lake is occupied by syen- 

 ites and felsites, succeeded in the upper half by the Silurian 

 strata, which form a band about seven miles long and three wide 

 terminating on the northern shore of the Upper Marie Joseph 

 Lake. There are several small outliers in this district, at Five 

 Islands Lake, and on the shores of Framboise Cove ponds. 



A line drawn from the head of Mira River to the shore at the 

 northern side of Catalogue Lake forms the extreme southern 

 boundary of these measures. This line passes within about a 

 mile and a half of the head of Gabarus Bay. While the Silurian 

 measures are unbroken in the northern part of this district along 

 the shore of the Mira River, they are broken into by isolated 

 ridges and projections of the Laurentian felsites, etc., of the 

 Gabarus district. Thus we find within and to the north of the 

 line running from the head of Mira to Catalogue, the felsites, etc., 

 of the White Granite Hills, the String- Lakes, Blue Mountains, 

 Bengal Lakes, and Catalogue Road. 



The stratigraphical arrangement of these measures cannot now 

 be made out with any degree of certainty. The plications im- 

 posed on the strata during succeeding ages, and the severe denu- 

 dation which has ploughed the island so deeply, have left the 

 sections imperfect. Generally speaking these measures are now 

 presented as imperfect folds, havdng a general north-east and 

 south-west course with cross foldings, having their origin in local 

 irregularities of the surface of the Laurentian rocks, upon which 

 they were deposited. It may also be inferred from the volume 

 of conglomerates, grits and coarse sandstones presented at several 

 8 



