No. IV. APPENDIX. 379 



yellow, and hornblende. This rock is massive and 

 eruptive at Cape M'Clure, lat. 72° 52' N., and occasion- 

 ally gneissose, as at lat. 72° 13' N. Between these two 

 points, at lat. 72° 37' N., a limestone bluff occurs con- 

 taining the characteristic Silurian fossils, and is suc- 

 ceeded at 72° 40' by a ferruginous limestone, bright 

 red, and a few beds of fine red sandstone, like those 

 observed by M'Chntock at Transition Valley, North 

 Somerset. The entire western portion of Prince of 

 Wales' Land is composed of Silurian limestone, which in 

 the extreme west, at Cape Acworth, becomes chalky in 

 character and non-fossUiferous, resembling the peculiar 

 Silurian limestone found on the west side of Boothia 

 Felix. 



II. — The Silurian Hocks. 



The Silurian rocks of the Arctic Archipelago rest 

 everywhere directly on the granitoid rocks, with a re- 

 markable red sandstone, passing into coarse grit, for 

 their base. This sandstone is succeeded by ferruginous 

 limestone, containing rounded particles of quartz, which 

 rapidly passes into a fine greyish green earthy lime- 

 stone, abounding in fossils, and occasionally into a 

 chalky limestone, of a cream colour, for the most part 

 devoid of fossils. The average dip of the Silurian lime- 

 stone varies from 0° to 5° N.N.W., and it forms occa- 

 sionally high cHffs, and occasionally low flat plains, 

 terraced by the action of the ice as the ground rose 

 from beneath the sea. The general appearance of the 

 rocks is similar to the Dudley limestone, and would 

 strike even an observer who was not a geologist. This 

 resemblance to the Upper Silurian beds extends to the 

 structure of the rocks on the large scale. Alternations 

 of hard limestone and soft shale, so characteristic of the 

 Upper Silurian beds of England and America, arranged 

 in horizontal layers, give to the cliffs around Port 



