1855.] ISBISTER NORTH AMERICA, ETC. 497 



May 16, 1855. 

 E. H. Hargraves, Esq. was elected a Fellow. 

 The following Communications were read : — 



^ 



I. On the Geology of the Hudson's Bay Territories, and oj 

 portions of the Arctic and North-Western Regions of 

 America ; with a Coloured Geological Map. 



By A. K. Isbister, M.A., M.R.C.P. &c. 



[Plate XIV.] 



[Contents.] 

 Introduction. 



Territories lEast of the Rocky Mountains. 



Physical Features ; and Range of the CrystaUine rocks. 



Central Plateau of CrystaUine Rocks. 



Silurian Basin of Hudson's Bay. 



Silurian Basin of Lake Winipeg. 



Devonian Formation of the Elk or Mackenzie River. 



Other Formations of the Mackenzie River Basin. 



Silurian Rocks of the Great Slave Lake and River. 



Carboniferous Series. 



Lignite Formation. 

 Elevatory Movements ; and Pleistocene Deposits. 



Territories West of the Rocky Mountains. 



Physical Features. 



Oregon Territory and Russian America. 



Fossils of the Carboniferous Formation. 



Jurassic Fossils. 



Tertiary Fossils. 



Fossils of the Drift. 



Introduction. — In submitting to the Society a Geological Map 

 of this extensive region, with a few explanatory remarks, my object 

 has been to recapitulate very concisely the various observations of 

 the geologists and travellers who have explored, and of the naturalists 

 who have examined the organic remains of, this portion of the Ame- 

 rican Continent, and to present as completely as possible the results 

 which have been hitherto attained in the study of its geological form- 

 ations. The numberless difficulties inherent in such an undertaking, 

 embracing a range of country so vast and so difficult to explore, or 

 even to obtain access to, must necessarily render any attempt of this 

 nature very imperfect ; but I have been induced to undertake it in 

 the belief that, in the absence of any general view of the geological 

 structure of this extensive but interesting region, even the most cur- 

 sory classification of its formations might be useful to those emplo}- ed 

 in developing the structure of the crust of the earth, — the more espe- 

 cially as it is not probable that the attention of practical geologists 

 will soon be directed to this distant and almost inaccessible field of 

 investigation. 



To render the present attempt as complete as the state of our 



