488 B. Hobson — Twelfth International 



of time, this pressure is released these substances will probably 

 effect a reversal of the original change. P. F. Fanning gave 

 "A contribution to the Metallogeny of the Philippine Islands", 

 and Dr. M. Maclaren a paper on *' The Persistence of Ore in. 

 Depth ". 



The fourth topic discussed was "The Origin and Extent of the 

 Pre-Cambrian Sedimentaries ". Dr. J. J. Sederholm in "Different 

 Types of Pre-Carabrian Unconformities" described the conditions in 

 Fenno-Scandia, and incidentally mentioned that "it seems that our 

 separation of the strongly metamorphic schists, near Lake Ladoga, 

 from the Kalevian proper, as a much older subdivision, designated 

 Ladogian, was founded on an erroneous correlation between the 

 post-Kalevian granites at Lake Ladoga and the younger pre-Kalevian 

 granites of Western Finland". In a second paper "On Regional 

 Granitization (or Anatexis) " Sederholm described palingenesis or 

 the formation of new rocks in Finland by the refusion i7i situ of 

 pre-existing igneous or sedimentary rocks. Professor G. A. J. Cole 

 gave " Illustrations of the Formation of Composite Gneisses and 

 Amphibolites in North- West Ireland". Professor W. S. Biiyley 

 described "The Pre-Cambrian Sedimentary Rocks in the Highlands 

 of New Jersey". Dr. G. F. Matthew dealt with "Cambrian and 

 Pre-Cambrian in the Maritime Provinces of Canada". 



The fifth subject discussed was "The Subdivisions, Correlation, and 

 Terminology of the Pre-Cambrian". Dr. A. Strahan gave an account 

 of "The Subdivisions and Correlation of the Pre-Cambrian Rocks of 

 the British Isles", and stated that we seem to lack justification for 

 attempting a chronological sequence of pre-Cambrian rocks in the 

 British Isles, further than is involved in placing the Lewisian gneiss 

 among the oldest, and the Torridonian among the later formations. 

 Dr. J. Home described the pre-Cambrian and Dalradian rocks of 

 Scotland. Professor A. C. Lawson read a paper on " A Standard 

 Scale for the Pre-Cambrian Rocks of North America", in which he 

 took the Lake Superior region as typical, and tabulated in ascending 

 order Coutchiching, Kewatin (grouped together as Ontarian), 

 Laurentian granite gneiss, batholithic in Ontarian, Unconformity, 

 Lower Huronian, Unconformity, Upper Huronian, Algoman granite 

 gneiss, batholithic in Huronian, Eparchceun Interval, Animikie, 

 Uyiconformity , Keweenawan (Nipigon), grouped together as Algonkian, 

 Unconformity^ Upper Cambrian (Potsdam). Mr. W. H. Collins, of 

 the Geological Sui-vey of Canada, in "A Classification of the Pre- 

 Cambrian Formations in the region east of Lake Superior ", 

 announced that the gap of 70 miles between the Sudbury and the 

 Cobalt districts has been investigated by the Geological Survey and 

 was closed last autumn so that the sequences in the two areas can 

 be correlated, and he gave a table of correlation. Professor A. P. 

 Coleman read a paper on " The Sudbury Series and its bearing on 

 Pre-Cambrian Classification ". The impression made upon the writer 

 by the discussion on American pre-Cambrian classification was that 

 hardly two authorities agree, and that the grouping ixnder the name 

 of Huronian of three or more systems, separatt'd by great uncon- 

 formities, only leads to confusion. Mr. E. Vredenburg and Sir T. H. 



