382 Robb on Superficial Deposits of Canada, 



ARTICLE. XXXV. — Some observations relating to the physical 

 condition of the superficial deposits in Canada, By Charles 

 Robb, Esq. C. E. Montreal. 



(Read before the Natural History Society^ Nov. 1862.) 

 I. 



The structure of the fundamental rocks of Western Canada 

 and their geographical boundaries, have been thoroughly ascer- 

 tained and defined by the Provincial geologists ; and from the 

 simplicity of that structure, the regularity of their sequence, and 

 the slight alteration both in position and mineral character, which 

 they have undergone since their original deposition, this part of 

 their task would have been comparatively easy, were it not for 

 the thick masses of clay^ sand and gravel which for the most part 

 envelop and conceal them. Athough the I>rift, as these superfi- 

 cial deposits are called, is one of the most recent of all the geolo- 

 gical formations, its date being immediately before the creation 

 of the existing species of organized beings, it seems remarkable 

 that its precise nature and origin should be less clearly under- 

 stood than those of the more ancient rocks on which it reposes. 

 Apart from the interest attaching to the subject in a purely scien- 

 tific point of view, its investigation is of the utmost practical im- 

 portance in an agricultural country like this ; as such knowledge 

 is calculated to render material aid in understanding the nature and 

 durability of our soils, and in determining the best methods of de- 

 veloping their resources and preventing their deterioration. To 

 these investigations, in so far as they refer to Lower Canada, Dr. 

 Dawson has devoted much attention and made many valuable 

 contributions, and in the Upper Province the researches of Pro- 

 fessor Chapman of Toronto, and of Mr. Robert Bell, under the di- 

 rection of Sir Wm. Logan, have thrown much light on the subject ; 

 and we may shortly expect to be put in possession of the result of 

 their combined labours in a lucid and condensed form by the 

 publication of Sir Wm. Logan's elaborate General Report on the 

 Geology of the Province. 



The three accomplished observers whom I have named agree, 

 upon independent grounds, in dividing the superficial deposits of 

 Canada into a lower and upper member ; the former consisting 

 chiefly of dark blue and greyish clays, the debris of the under- 

 lying limestone, and nearly destitute of boulders ; and the latter 

 of sand and gravel of granitic and gneissoid origin, with numerous 



