THE PERMO-CARBONIFEROUS. 39 



usually more hardened and altered than those of the Middle Coal 

 formation, and the latter more than those of the Upper Coal formation. 

 Moreover, there are instances in Nova Scotia of local unconformability 

 of the Lower Carboniferous beds ; and the New Glasgow conglomerate 

 afiords evidence of extensive denudation of the Lower Carboniferous 

 before the deposition of the productive Coal-measures. These facts 

 indicate the long duration of the Carboniferous period and the extent 

 of the physical changes which it included; and it is evident that, 

 had unconformability or extensive local denudation occurred some- 

 what higher in the system, it might have been regarded as forming 

 the base of an overlying Permian series. 



Detailed descriptions and sections of the Permo-carboniferous beds 

 as they occur at Gallas Point, Governor's Island, and Campbellton, 

 in Prince Edward Island, are given in the Report above referred to. 



7. THE CARBONIFEROUS. 



With reference to the structure and stratigraphy of the Carboni- 

 ferous, a large amount of work has been done by the officers of the £> 

 Geological Survey, principally in the Cape Breton, Pictou, and Cum- 

 berland areas, and more especially in the productive Coal-measures. 

 Much has also been done by private explorations, and the results are 

 so voluminous that I can scarcely do more than refer to the Retorts 

 in which the principal of them are contained. 



Discoveries in different Coal-Fields. 

 In the Report of the Geological Survey for 1872-3, Messrs Bailey 

 and Matthew have given details of the Coal-field of New Brunswick, 

 derived both from surveys and from borings made by Mr Ells. The 

 most remarkable general result is the small thickness of this widely- 

 extended Coal formation area. The estimate given is as follows, in 

 ascending order : — 



Gray sandstones and shales, equivalent of Mill-") 200 feet 



stone-grit . . . • • . j 



Coal-measures containing no known bed thicker ") 200 



than 26 inches . . . . . ) 



Upper Coal formation ..... 200 „ 



600 „ 



Perhaps there should be added to this a small additional thickness 

 for the Permo-carboniferous of the shore of Northumberland Strait. 

 But in any case it presents a great contrast to the vast thickness of 



