486 B. Hobso7i — Twelftli International 



II. — The Twelfth Inteenational Geological Congress in Canada. 

 By B. HOBSON, M.Sc, F.G.S. 



AT the Stockholm meeting of the Congress in 1910 an invitation 

 to hold the twelfth meeting in Canada was accepted. As the 

 Congress met in the United States in 1891 and in Mexico in 1906, 

 members were thus afforded an opportunity of visiting all the great 

 divisions of North America. The Canadian meeting was held at 

 Toronto from August 7 to 14, 1913, under the presidency of 

 Professor F. D. Adams, of McGill University. About 600 members 

 attended it, although the total enrolled was nearly twice as great, and 

 46 countries were represented among the members. The Congress 

 was formally opened by the Right Hon. Sir Charles Fitzpatrick, on 

 behalf of H.R.H. the Duke of Connaught, the Honorary President, 

 ■who was unavoidably absent, and speeches of welcome were made by 

 others. Dr. R. W. Brock, Director of the Geological Survey of 

 Canada and General Secretary of the Congress, presented to the 

 Congress a monograph entitled " The Coal Resources of the World", 

 the result of an inquiry made upon the initiative of the Executive 

 Committee of the Twelfth Congress, with the assistance of Geological 

 Surveys and mining geologists of different countries. It consists of 

 three quarto volumes of about 400 pages each (11 by Scinches) 

 and an atlas of 66 pages of maps in colours (13i by 19| inches) 

 published by Morang & Co., of Toronto, at $25 per set, net. It 

 forms a fitting companion to the volume on the Iron Ore Resources 

 of the World, published under the auspices of the Stockholm 

 Congress. 



In the second circular of invitation to the Toronto Congress seven 

 topics were mentioned as having been selected by the Executive 

 Committee as the principal subjects of discussion. The first of these 

 was "The Coal Resources of the World". Not much was said on 

 this subject, no doubt owing to those best qualified to speak having 

 given their views in the monograph. The second subject was 

 "Differentiation in Igneous Magmas". On this subject Professor 

 R. A. Daly read a paper entitled "Sills and Laccoliths illustrating 

 Petrogenesis ". He advocated gravitative differentiation and tabulated 

 seventy different sills and laccoliths, in twenty-nine of which he 

 maintained that such differentiation is shown. He also maintained 

 that many species of igneous rocks are due to large-scale assimilation 

 of country rocks by overhead or other stoping, giving rise to syntectic 

 magmas. Dr. A. Harker followed with a paper on " Fractional 

 Crystallization the Prime Factor in the Differentiation of Rock 

 Magmas ", in which he pointed out that a rock magma at a temperature 

 below that of the upper part of the temperature range of crystallization 

 must be pictured as an open fabric or sponge of crystalline matter 

 with interstices occupied by liquid magma. Under crustal stresses 

 the interstitial liquid may be squeezed out and thus differentiation 

 may arise, as the crystalline and liquid parts necessarily differ in 

 composition. A stratification and differentiation may also be brought 

 about by gravity acting upon a wholly fluid magma or (more 

 effectively) by the sinking of crystals in a magma still mainly fluid. 



