Alii in oJ y 4,5 



Greuville Series uncomformably, is now stated by Adams 



to consist of eruptive matter, mainly composed of triclinic 

 or lime felspars, and to which the name Anorthosite 1 may 

 properly be applied. These rocks, cutting the Greuville 

 Series, and apparently in some places, interbedded with 

 it, are not now regarded as a distinct series of beds, but 

 as indicating local outbursts of igneous action dating about 

 the close of the Greuville period. What aqueous rocks 

 may have been contemporaneous with these, or may have 

 filled the interval between the Greuville Series and the 

 Huronian. we do not at present certainly know, though 

 ably some of the rocks associated with the upper part 

 of the Laurentian, or the lower part of the Huronian in 

 the interior, and in the eastern part of Canada, may come 

 into this place. 2 



It is to be observed that in I860 these facts respecting 

 the fundamental gneiss and the Upper Laurentian of 

 Loean. were not distinctly before our minds, though in 

 subsequent papers I thought it best to consider the Greu- 

 ville group as a distinct series under the name " Middle 

 Laurentian." It is quite possible, however, that our 

 referring in the first instance to the Laurentian as a whole 

 may have led to erroneous impressions. 



For the purpose of these notes, therefore,, it will be best 

 and most accurate to confine ourselves to the Greuville 

 Series, which has been carefully explored and mapped by 

 the officers of the Geological Survey in the country lying 

 north of the Ottawa River, and also in some parts- of the 

 areas between that river and the St. Lawrence. In these 

 regions Logan recognized a thickness of 17,250 feet of 

 deposits, of which no less than 4.750 feet consisted of 

 limestone, principally in three great bands, though with 

 intercalated gneissose layers. The Greuville Series may 



1 Proposed by Hunt. 



2 Some of these beds are regarded by Von Hise (Jour, of Geology. Vol. i.) as a 

 lower member of the Huronian. They maybe identical in part with the "Kewatiu " 

 group of Lawson. 



35 



