﻿Book Notices. 457 



undoubtedly caused by some irregularities in the cooling of the 

 '•original inaguia, for which it is now difficult to find a satisfactory 

 •explanation," and further on he writes, the " streaks show a tendency 

 to merge into one another as though they had been produced by 

 motion in a liquid or plastic mass." 



The streaking is well developed at other areas, notably in the 

 .Saguenay anorthosite, near Chicoutimi, which shows all gradations, 

 from the massive to the well banded. 



The granulated variety is composed of large Tragments of plagio- 

 •clase, in a fine grained ground mass of the same mineral. The stages 

 illustrating the transition from non-granulated to the above is shown 

 in an excellent manner by three microphotographs. In the first 

 the rock is massive, the plagioclase being twinned polysynthetically ; 

 there are no strain shadows and just a trace of granulation in the 

 lower part of the section. In the next the felspar individuals are 

 much cracked, giving off broken grains, the twin lines are twisted and 

 strain shadows are present, but no foliation. The third shows the 

 remainder of a large crystal of felspar in the centre of the field which 

 has furnished the ground mass of smaller grains, presenting a distinct 

 foliation. The strain shadows appear in the large grains, but not in 

 the small ones, for as soon as the pressure is sufficient to break a 

 particle from its parent inass, the strain ceases and the shadow conse- 

 quently disappears. So it is only by having such examples as the last 

 described that it is possible to say definitely how the granulation was 

 produced. In this variety the plagioclase is white, the reason of 

 it being that the motion caused by pressure allows the free play of the 

 constituents of the rock, by which means the iron ore which was 

 disseminated through the felspar in the form of small grains becomes 

 concentrated in certain spots. 



When weathered this rock resembles crystalline limestone in a 

 iremarkable manner. In the south-east arm the hills protrude through 

 the drift, as white rounded knobs, thus giving to this section of 

 the country a characteristic of landscape peculiar to itself. 



Minor intrusions occur at Lakefield, St. Jerome and in the townships 

 •of Kildare, Cathcart and Brandon, An interesting fact in connection 

 with the position of the above rocks is that they occur along the edge 

 •of the Archcean Protaxis, which, in Cambrian time, bordered on 

 the ocean. The modern volcano follows the same law as its primaeval 

 prototype. 



Considerable attention has been given to the economic geology, with 

 the result that the following minerals have been found, some of which 

 are of importance : Magnetite, ilmenite, bog ore, ochre, graphite, 

 -apatite, mica, garnet rock, crystalline limestone and anorthosite. 

 The latter makes a good paving stone, and has been used for that 

 purpose in Montreal. No traces of gold or silver were discovered, 



