﻿142 PEOF. F. DAWSON ADAMS ON THE [May I908, 



A detailed description of this alteration, with a chemical and 

 mineralogical study of the transitional rocks, will be found in the 

 Report to which reference has already been made (p. 130). 



Evidences of the alterations of the third class are less frequent 

 and less striking. Nevertheless, in certain cases it appears to be 

 practically certain that there has been a distinct solution of the 

 invaded rocks by the granite. This, however, probably took place 

 on a comparatively small scale. 



An occurrence of this kind is found on the southern extension of 

 Kasshabog Lake, in the township of Methuen. Here the banded 

 amphibolite is invaded by the granite-gneiss, which has broken it 

 into fragments and partly dissolved some of them, giving rise to 

 a greyish, streaky-looking mass of irregular composition, much 

 lighter in colour than the amphibolite and darker than the granite, 

 being grey instead of reddish (see PL XI). 



Other examples of the same phenomenon, but on a larger scale, 

 may be seen at many places about the margin of the Anstruther 

 bathylith. At the northern end of this occurrence, where the 

 granite-gneiss of the bathylith runs up into the township of 

 ITonmouth, it is bounded on the north by an extension of what 

 is known as the Catcheeoma Gneiss. This is a basic rock, 

 which resembles in appearance a light-coloured amphibolite. To 

 the north of the Catcheeoma Gneiss is a dark amphibolite, and 

 then a band of limestone. The granite-gneiss, elsewhere red, 

 becomes grey in colour and poor in quartz as this northern 

 boundary is approached, and passes into the Catcheeoma Gneiss, 

 which is at first seen to hold a few tear-shaped inclusions of the 

 amphibolite ; these become increasingly numerous as the contact 

 is approached where the amphibolite is reached, through which 

 there run streaks of the invading rock. Evidently the amphi- 

 bolite has been partly dissolved by the granite-magma, and the 

 Catcheeoma Gneiss here consists apparently of the granite-magma 

 rendered basic by the solution of amphibolite. 



YIII. Distribution and Thickness of the Grenville Series. 



In an area where the geological structure is so complicated, and 

 where the strata have been invaded by such immense bodies of 

 igneous material, it is difficult to determine the true succession and 

 thickness of the sedimentary series. As will be seen, however, by 

 consulting the accompanying map (PI. XIII), the area is traversed 

 by the Hastings road, which for a distance of 25*3 miles passes con- 

 tinuously across the limestones and amphibolites of the Grenville 

 Series, and throughout this whole distance crosses these rocks 

 nearly at right angles to their strike. 



Furthermore, throughout the whole distance these strata dip in 

 a southerly direction at high angles. Here and there, at long 

 intervals and for a few yards, a reversed or northerly dip can be 

 observed ; but this is merely local, owing to a minor undulation in 

 the strata, and has no stratigraphical significance. The angle of 



