TRANSACTIONS OF SECTION C — PRESIDENTIAL ADDRESS, 591 



Section C— GEOLOGY 



President of the Section. — Professor A. P. Coleman, M.A., Ph.D., 



F.R.S. 



THURSDAY, SEPTEMBER 1. 

 The President delivered the following Address :— 



The History of the ' Canadian Shield.'' 



Can there be any greater contrast than Pleistocene boulder clay resting on 

 Archaean gneiss, the latest of rocks covering the earliest, with almost the whole 

 known history of the world in the interval between ? It is a fascinating occupa- 

 tion for a geological dreamer to sit on some hillside in Scotland or Finland or 

 Northern Canada, where the schists and gneisses rise in rounded ridges or bosses 

 through boulder clay, and ponder on all the strange happenings that separate the 

 clay from the rock beneath. 



The clay melting from its enclosed boulders under the frosts and rain seems 

 the very emblem of the fleeting things of yesterday ; while the Archaean gneiss 

 and greenstones are the type of the solid, imperishable framework of the earth, 

 on which all the later rocks rest. 



The boulder clay recalls the white surface of a Continental ice-sheet with 

 summer blizzards sweeping across it like those of the Antarctic tableland ; while 

 the gneiss beneath tells of a molten magma cooling during millions of years 

 beneath miles of overlying rock. 



It is the meeting-place of the geological extremes, and their contact marks 

 the greatest of all discordances. 



One thing the clay and the gneiss have in common — both were long neglected 

 by geology; the Pleistocene beds because they were not rocks, but only 'drifts,' 

 confused and troublesome things, hiding the real rocks, the orderly stratified for- 

 mations ; the 'basal complex' because its schists and gneisses were fossil-less, com- 

 plex, and mysterious products of the dim beginnings of a world still ' without 

 form and void.' The molten sphere, with its slowly consolidating crust, belonged 

 rather to the astronomer than the geologist. 



Geology has, of course, long lost that attitude, and now finds some of its most 

 seductive problems in these once neglected extremes of the earth's history. Those 

 who distrust the ' glacial nightmare ' are now very few in number ; but there 

 are still revered veterans, like Professor Rosenbusch, who speak of the Archasan 

 gneisses as parts of the earth's Erstarrungskruste, and who frame theories of the 

 earth's cooling and wrinkling in its hot and furious youth. 



Over more than half of Canada the field geologist is forced to occupy himself 

 with both the Pleistocene and the Archaean, since the two are almost everywhere 

 together, while the fossil-bearing beds of the vast intervening time are absent. 

 The seemingly unnatural conjunction is not entirely without advantages, for the 

 Pleistocene has furnished the clue to certain very puzzling problems of the 

 Archaean, as will be shown later. 



The geologists of the world have long known the broad outlines of the 

 Canadian Archaean or Pre- Cambrian area through Suess's masterly portrayal of 



Q Q 2 



