218 Canadian Record of Science. 



be steadily kept in view that many of the old p re-Cambrian 

 crystalline rocks must have been different originally from 

 those succeeding them, and that, consequently, these last, 

 even when metamorphosed, present different characters. 



I may remark here that, though a palaeontologist rather 

 than a lithologist, it gives me great pleasure to find so much 

 attention now given in this country to the old crystalline 

 rocks, and to their study microscopically and chemically as 

 well as in the field, a work in which Sorby and Allport were 

 pioneers. As a pupil of the late Professor Jameson of 

 Edinburgh, my own attention was early attracted to the 

 study of minerals and rocks as the stable foundations of 

 geological science; and so far back as 1841 I had learnt of 

 the late Mr. Sanderson, of Edinburgh, who worked atlSTicol's 

 sections, 1 how to slice rocks and fossils ; and since that time 

 I have been in the habit of examining everything with the 

 microscope. The modern developments in this direction are 

 therefore very gratifying to me, even though, as is natural,- 

 they sometimes appear to be pushed too far or their value 

 over-estimated. 



That the older gneisses were deposited, not only in what is 

 now the bed of the Atlantic, but also on the great continental 

 areas of America and Europe, anyone who considers the 

 wide extent of these rocks represented on the map recently 

 published by Professor Hull can readily understand. 2 It is 

 true that Hull supposes that the basin of the Atlantic itself 

 may have been land at this time, but there is no necessity 

 for holding this view, more especially as the material of the 

 gneiss could not have been detritus derived from sub-aerial 

 decay of rock. 



Let us suppose, then, the floor of old ocean covered with 

 a flat pavement of gneiss, or of that material which is now 

 gneiss, the next question is how and when did this original 

 bed become converted into sea and land. Here we have some 

 things certain, others most debateable. That the cooling 

 mass, especially if it was sending out volumes of softened 

 rocky material, either in the exoplutonic or in the crenitic 



1 Trans. Royal Irish Academy. 2 And I believe at Withani's also. 



