﻿310 Canadian Record of Science. 



invaded by intrusions of the latter series when this was in 

 a senii-niolten or plastic condition. The limestones, while 

 themselves rendered more or less plastic by the same heat 

 which softened the lower gneisses, do not show any 

 distinct evidence of absorption or solution by the invading 

 rocks, unless some of the highly garnetiferous gneisses 

 usually associated with the limestones are formed by a 

 commingling of the two rocks. Masses of the highly 

 crystalline limestone or marble in some cases lie quite 

 isolated in what are, to all appearances, the lower gneisses, 

 as if they had been separated from the parent mass, and 

 had passed outward or downward into the gneissic magma. 



The contact of the Fundamental Gneiss and the 

 Grenville series would appear therefore to be a contact of 

 intrusion, in very many cases at least. 



The question of the relations of the Grenville series to 

 the Hastings series then presents itself. Although 

 repeated traverses have been made from one series into 

 the other, no sharp line of division has been found. 

 Towards the south-east the limestones of the Grenville 

 series in many places, though still highly crystalline, 

 seem to be less highly altered, and finally, as the Hastings 

 series is approached, present in places the bluish color 

 of the limestones of the latter series ; so that it is often 

 impossible to determine to which series they should 

 be referred. The limestones of both series also have the 

 numerous small interstratified gneissic inclusions or 

 bands so frequently referred to in the descriptions of the 

 limestones of the Grenville series, making the resemblance 

 still more complete. In fact, although the true relations 

 of the two series are obscured by the presence of numerous 

 great intrusions of granitic and basic pyroxenic rocks, and 

 can only be determined with absolute certainty by the 

 completion of the mapping, the investigations so far 

 indicate that in the region in question the Hastings series 

 would seem to represent the Grenville series in a less 



