440 THE DIVISION OF THE AZOIC ROCKS OF CANADA 



tion, the parallelism that can be shewn to exist between their Inhologi- 

 cal character, and that of metamorphic rocks of a later age, leaves no 

 doubt on my mind that they are a series of very ancient sedimentary 

 deposits in an altered condition. The further they are investigated the 

 greater is the evidence that they must be of very great thickness, and 

 the more strongly is the conviction forced upon me, that they are 

 capable of division into stratigraphical groups, the superposition of 

 which will be ultimately demonstrated, while the volume each will be 

 fomid to possess, and the importance of the economic materials by 

 which some of them are characterized, will render it proper and con- 

 venient that they should be recognised by distinct names, and repre- 

 sented by different colors on the geological map. 



So early as the year 1845, as will be found by reference to my 

 report on the Ottawa district, presented to the Canadian Government 

 the subsequent year, a division was drawn between that portion which 

 consists of gneiss and its subordinate masses, and that- portion consist- 

 ing of gneiss interstratified with important bands of crystalline lime- 

 stone. I .was then disposed to place the lime-bearing series above the 

 uncalcareous, and although no reason has since been found to contra- 

 dict this arrangement, nothing has been discovered especially to 

 confirm it ; and the complication which subsequent experience has 

 shewn to exist in the folds of the whole, — apparent dips being from 

 frequent overtures of little value, — would induce me to suspend any 

 very positive assertion in respect to their relative superposition, until 

 more extended examination has furnished better evidence. 



In the same report is mentioned, among the Azoic rocks, a formation 

 occurring on Lake Temiscamang, and consisting of Siliceous slates 

 and slate conglomerates, overlaid by pale sea-green or slightly greenish- 

 white sandstone, with quartzose conglomerates. The slate conglo- 

 merates are described as holding pebbles, sometimes a foot in diameter, 

 derived from the subjacent gneiss, the boulders displaying red feldspar, 

 translucent quartz, green hornblende, and black mica, arranged in 

 parallel layers, which present directions according with the attitude in 

 which the boulders were accidentally enclosed. From this it is evident 

 that the slate conglomerate was not deposited until the subjacent for- 

 mation had been converted into gneiss, and very probably greatly 

 disturbed ; for while the dip of the gneiss, up to the immediate vicinity 

 of the slate conglomerate, was usually at high angles, that of the latter 

 did not exceed nine degrees, and the sandstone above it was nearly 

 horizontal. 



In the report transmitted to the Canadian Government, in 1848, on 

 the north shore of Lake Huron, similar rocks are described as consti- 



