24 Canadian Record of Science. 



grains partially interlocking and having very irregular 

 outlines. The rock seems, in fact, to have approached 

 very closely, both in structure and in composition, to the 

 gneiss which lies near it. 



Mechanical separations by means of Thoulet's solution 

 were made of all the specimens. No attempt was made 

 to separate the dark constituents, however, as a sufficient 

 idea of their relative abundance could be had with the 

 aid of the microscope. The following table, in which the 

 figures represent percentage by weight, is arranged in 

 order of the amount of basic constituents present. 

 When the loss attendant on crushing (to 80-mesh) and 

 washing of the powder, and the necessary error due to 

 interposition of the constituent grains are considered, it 

 is fully appreciated that the method by no means justifies 

 the use of decimals, if, in fact, the units are reliable ; but 

 instead of making round numbers of them, it was thought 

 at least as accurate, and perhaps wiser to record the 

 actual results obtained. It may be noted that in the 

 case of a crop of composite grains falling between the 

 specific gravities of two minerals, half its weight was 

 added to the weight of the crop of each mineral. 



In the column at the left are the numbers of the 

 different specimens, corresponding to the thin sections. 

 In order to show the nature of the rocks without being 

 obliged to turn back to the descriptions, the following 

 symbols have been used : — 



+ Gneissic Granite, 



x Gray Gneiss. 



+ Altered Limestone. 



* x Inclusion. 



In the column under Basic Constituents, the different 

 minerals are represented thus : A — Augite, B — Biotite, 

 H — Hornblende ; and where two minerals are present, 

 B & H indicate that the two are present in about equal 



