26 Canadian Record of Science. 



amounts, B > H, more biotite than hornblende, and 

 A « H, much more hornblende than augite, etc. 

 Wherever a mineral has been found, but in amount too 

 small to determine quantitatively, a dash is placed. 



In the granite, the gray gneisses, and sometimes in the 

 inclusions, the feldspar is seen to be acid, while in the 

 altered limestones and the other inclusions it is richer in 

 lime, and consequently of higher specific gravity. Another 

 noticeable fact is that as the amount of calcite — the 

 remains of the limestone — decreases in the altered lime- 

 stones, the augite, which is richer in lime, gives way to 

 hornblende which is poorer; and in the rock containing 

 the most hornblende, that is, the one farthest removed, as 

 regards composition, from the limestone, orthoclase 

 appears. The pyroxene is probably especially rich in 

 lime in this case, since it is so pale in color. In the 

 altered limestones, the color of the hornblende is not very 

 deep green, indicating a high percentage of lime, but in 

 the gray gneisses and inclusions it is generally quite dark, 

 and often brownish, pointing to the presence of more iron, 

 magnesia, etc. The range in the character of the inclu- 

 sions is also noteworthy, one having practically the same 

 composition as the gray gneisses, and another resembling 

 the most basic or most altered of the altered limestones. 



HYPOTHESES AND DISCUSSIONS OF THE ORIGIN AND 



RELATIONS OF THE VARIOUS ROCKS. 



e 

 Further consideration of the genetic relations of thes 



rocks may now properly be entered upon ; and im- 

 mediately are recalled the two questions proposed at the 

 outset, viz., the origin of the basic rocks at the contact, 

 and the real nature of the dark streaks and patches held 

 by the gneissic granites. If these could be settled, the 

 solution of the whole problem here involved would be 

 well under way. 



The first question may be still farther limited to this : 



