PETEOGEAPHY OF ONTAEIO. 59 



So far as special constituents are concerned, it is noticeable how prevalent the mineral 

 hornblende is in our rocks, forming an essential ingredient in the great majority of basic 

 rocks and in fully half of the acid ones. The only series in which it is rare is the small 

 one of the limestones and dolomites. 



The widespread occurrence of microline is also worthy of remark. That this is true 

 of other parts of the Dominion is shewn by sections of granite and gneiss in my collection 

 from the Selkirks in British Columbia. Though differing much in habitus from those of 

 Ontario, they almost all contain large quantities of the mineral. 



The presence of a considerable group of rocks containing scapolite as an essential 

 mineral seems worthy of special notice. The writer is informed that similar rocks have 

 been described by Michael-Levy, Brogger and others ; and that Mr. F. D. Adams contri- 

 buted at the Montreal Meeting of the British Association a paper on Canadian rocks of the 

 kind, an abstract of which was published in the Proceedings of the Association. Unfor- 

 tunately the literature on the subject is not at my command, so that it is impossible at 

 present to compare the scapolite rocks of our drift with those described by the disting- 

 uished petrographers mentioned. 



For the convenience of reference there will be found on the opposite page a tabular 

 list of the massive and schistose rocks described in this paper. 



EXPLANATION OF PLATES. 

 Plate I. 



(All between crossed niçois anj ma;^ified 85 diameters.) 



Fig. 1. — Augite with zones of decomposition products. 



Fig. 2. — Epidote in weathered plagioolase. 



Fig. 3. — Transition from orthoclase to microline. 



Fig. 4. — Scapolite, longitudinal section red and green, cross section dark grey, 



Plate IL 



(Figs. 1, 2 and 3 with the lower nicol only : fig. 1 between crossed niçois. All magnified 85 diameters.) 



Fig. 1. — Cross section of bluish green augite and hornblende with chief axis in common; also brown titanite. 



Fig. 2. — Augite and hornblende as in fig. 1, but longitudinal section. 



Fig. 3. — -Diallage (yellow) enclosing bluish hypersthene and brown hornblende. 



Fig. 4. — Intergrowth of orthoclase and plagioclaso (niieroperthite?) 



