222 Canadian Record of Science. 



Thus in the later Eozoic and early Palaeozoic times, which 

 succeeded the first foldings of the oldest Laurentian, great 

 ridges were thrown up, along the edges of which were beds 

 of limestone, and on their summits and sides, thick masses 

 of ejected igneous rocks. In the bed of the central Atlantic, 

 there are no such accumulations. It must have been a flat, 

 or slightly ridged, plate of the ancient gneiss, hard and 

 resisting, though perhaps with a few cracks, through which 

 igneous matter welled up, as in Iceland and the Azores in 

 more modern times. In this condition of things we have 

 causes tending to perpetuate and extend the distinctions of 

 ocean and continent, mountain and plain, already begun ; 

 and of these we may more especially note the continued 

 subsidence of the areas of greatest marine deposition. This 

 has long attracted attention, and affords very convincing 

 evidence of the connection of sedimentary deposit as a cause 

 with the subsidence of the crust. l 



We are indebted to a French physicist, M. Faye, 2 for an 

 important suggestion on this subject. It is that the se- 

 diment accumulated along the shores of the ocean presented 

 an obstacle to radiation, and consequently to cooling of the 

 crust, while the ocean floor, unprotected and unweighted, 

 and constantly bathed with currents of cold water having 

 great power of convection of heat, would be more rapidly 

 cooled, and so would become thicker and stronger. This 

 suggestion is complementary to the theory of Professor 

 Hall, that the areas of greatest deposit on the margins of 



1 Dutton in Report of US. Geological Survey, 1881. From facts 

 stated in this report and in my Acadian Geology, it is apparent that 

 in the Western States and in the coalfields of Nova Scotia, shallow- 

 water deposits have been laid down, up to thicknesses of 10,000 to 

 20,000 feet in connection with continuous subsidence. See also a 

 paper by Ricketts in the Geol. Mag. 1883. It may be well to add 

 here that this doctrine of the subsidence of wide areas being caused 

 by deposition, does not justify the conclusion of certain glacialists 

 that snow and ice have exercised a like power in glacial periods. 

 In truth, as will appear in the sequel, great accumulations of snow 

 and ice require to be preceded by subsidence, and wide continental 

 areas can never be covered with deep snow, while, of course, ice can 

 cause no addition of weight to submerged areas. 



2 Revue Scientifique, 1886. 



