CU PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



syenites, and intrusive diorites are also met with. The second Azoic 

 system occurs on the banks of Lakes Huron and Superior, and con- 

 sists of a series of schists, grits, Hmestones, and conglomerates, inter- 

 stratified with thick beds of diorite, and rest unconformably on the 

 Laurentian System. Mr. Logan gives it the name of Cambrian or 

 Huronian System. It abounds with metalliferous veins, which have 

 hitherto been but little worked. 



On the islands to the north of Lake Huron is a series of fossili- 

 ferous beds, resting horizontally on the inclined strata of the Hu- 

 ronian System. Further south they rest directly on the rocks of the 

 Laurentian System. They correspond with Murchison's Lower Silu- 

 rian, and are overlaid by the Upper Silurian, Devonian, and Carboni- 

 ferous systems. These groups occupy the whole of the Canadian 

 portion of the great basin bounded on the north by the Laurentian 

 and Huronian formations. 



Mr. Logan has pointed out that this basin is separated into two 

 portions by an anticlinal axis, vs^hich, following the valley of the 

 Hudson and Lake Champlain, enters Canada near the Bay of Mis- 

 iscoui, and running thence N.E., reaches the St. Lawrence near 

 Deschambault, ten leagues west of Quebec. The rocks of these two 

 basins present a very remarkable difference, both in their physical 

 and chemical aspect. The formations of the western basin are almost 

 horizontal, and perfectly conformable, whilst in that to the east there 

 is a want of conformity between the Upper and Lower Silurian, and 

 between the Devonian and Carboniferous systems. The various 

 strata of the eastern basin are, moreover, much twisted and contorted, 

 and have in some places undergone great chemical and mineralogical 

 metamorphism. A glance at the map at once points out this im- 

 portant difference. The conclusion is irresistibly forced upon us, 

 that, while on the western side the different systems succeeded one 

 another gradually and conformably, violent convulsions, occurring at 

 certain epochs, on the eastern side, interfered with the tranquil suc- 

 cession of the deposits ; and we see that, although these breaks 

 occurred between the Upper and Lower Silurian periods, and between 

 the Devonian and Carboniferous systems, they were still only local 

 phsenomena ; and that, however they may have affected the condition 

 of life in the neighbouring seas, they produced no effect on the regular 

 succession of deposits even in their immediate vicinity. It would be 

 difficult to find anywhere a better example of the necessity of not 

 attaching too great an importance to those breaks which occur in 

 other regions, and which, after all, may have only a local signifi- 

 cance. 



Mr. Logan then proceeds to describe the different features of these 

 two basins, the western and the eastern, adding an account of the 

 metamorphic rocks, and of the post-tertiary and alluvial deposits. 



The volume of Mr. J. W. Dawson, entitled 'Acadian Geology,' 

 being an account of the geological structure and mineral resources of 

 Nova Scotia and portions of the neighbouring provinces of British 

 America, must also be noticed. The author has endeavoured to com- 

 bine two great desiderata ; while striving to make his work sufficiently 



