3i 



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. 



Other examples of the same phenomenon, but on a 

 larger scale, may be seen at many places about the margin 

 of the Anstruther batholith. At the northern end of this 

 occurrence, where the granite-gneiss of the batholith runs 

 up into the township of Monmouth, it is bounded on the 

 north by an extension of what is known as the Catch- 

 ecoma gneiss. This is a basic rock which resembles in 

 appearance a light-coloured amphibolite. To the north 

 of the Catchecoma 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 the 

 northern boundary is approached, and passes into the 

 Catchecoma 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 amphibolite 

 has been partly dissolved by the granite magma, and 

 here the Catchecoma gneiss consists apparently of the 

 granite magma rendered basic by the solution of amphi- 

 bolite. 



VII. — Distribution and Thickness of the Grenville 



Series. 



In an area where the geological structure is so com- 

 plicated, and where the strata must have been invaded 

 by such immense bodies of igneous material, it is difficult 

 to determine the true succession and thickness of the 

 sedimentary series. The area is traversed by the Hastings 

 road, which for a distance of 25-3 miles (40-7 km.) passes 

 continuously across the limestones and amphibolites of 

 the Grenville series, and throughout this whole distance 

 crosses these rocks nearly at right angles to their strike. 



