68 C Canadian Record of Science. 



Oiitremont. This rock is a nepheline syenite, and con- 

 tains so much nepheline that if a little of it be finely 

 powdered and boiled with acid for a few minutes it will 

 pass into a mass of thick jelly. 



The final outburst of volcanic energy on the part of 

 Mount Royal is represented by the swarm of narrow 

 dykes or walls of igneous rock which cut not only through 

 the limestones of the region but also through the rocks of 

 both of the former eruptions just referred to. These, 

 although erupted during the final stage, are not all abso- 

 lutely identical in age ; in fact, in the excavation made 

 for the reservoir on Peel Street some seven distinct sets 

 of dykes, each cutting across, and therefore more recent 

 than the previous ones, could be seen. These dykes are 

 composed of a variety of rocks ; all of them are very rare 

 and found in but few otlier places in the world. 



Now, although detailed study of these rocks requires 

 some special knowledge of the methods of modern petro- 

 graphy, no study of the region can be made until the 

 necessary materials for it have been collected. The col- 

 lection of such materials, in itself an occupation by no 

 means devoid of interest, might easily be undertaken by 

 members of the Society, and the collections, if carefully 

 labelled and deposited in the Society's Museum, would 

 always be available for detailed study. Such a detailed 

 study is now being undertaken by Dr. Harrington and 

 the writer, who would be glad to examine and describe 

 any carefully collected material. 



It is from the dykes of the third eruption that collec- 

 tions of the greatest value can be made, especially where 

 these are exposed from time to time in cuttings and exca- 

 vations which are subsequently filled in again, and the 

 exposures thus rendered inaccessible. In collecting speci- 

 mens from such dykes, the width of the dyke, measured 

 across it, that is, at right angles to its dip, if it be not 

 vertical, should be noted, as also the direction in which 



