256 American Association. 



stratigrapliical groups, the superposition of wliich will be ultimate- 

 ly demonstrated ; while the volume each will be found to possess, 

 and the importance of the economic materials by which some of 

 them will be characterised, will render it proper and convenient 

 that they should be recognized by distinct names, and represented 

 by different colors on the geological map. So early as the year 

 1845, as will be found by my report on the Ottawa district (pre- 

 sented 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 consisting of gneiss inter- 

 stratified with important bands of crystalline limestone. I was 

 disposed to place the lime-bearing series above the uncalcareous, 

 and although no reason has since been found to contradict this 

 arrangement, nothiug has been discovered especially to confirm it : 

 while the complication which subsequent experience has shewn to 

 exist in the folds of the whole, (apparent dips being from frequent 

 overturns, of little value,) would induce me to suspend any very 

 positive assertion in respect to their relative super-position, until 

 more extended examination has furnished better evidence. In the 

 same report is mentioned among the azoic rocks, a formation oc- 

 curring on Lake Temiscaming, and consisting of silicious slates and 

 slate comglomerates, overlaid by pale sea-green and slightly green- 

 ish-white sandstone with quartzoss conglomerates. The slate 

 conglomerates are described as holding pebbles and boulders 

 (sometimes one 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 deflections, 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 forma- 

 tion 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 constituting the group v/hich is 

 rendered of such economic importance from its association with 

 copper lodes. This group consists of the same silicious slate and 

 slate conglomerate, holding pebbles of syenite instead of gneiss, 

 similar sandstones, some of them tinged green, and similar quart- 



