The Monteregian Hills. 209 



Trenton limestone on the flank of Mount Royal during 

 the construction of the Montreal Reservoir extension. 

 Dykes, in fact, abound wherever in the vicinity of Mount 

 Eoyal the bed rock is exposed by the removal of the 

 drift, as for instance, at the Mile End Quarries, St. Helen's 

 Island, and in the bed of the St. Lawrence about Point St. 

 Charles when it is exposed at low water. The whole dis- 

 trict about the city would present a network of dykes, 

 could the overlying drift be removed. 



Dresser mentions dykes as occurring abundantly about 

 Shefford mountain. In Mount Johnson, on the other 

 hand, they are almost entirely absent. Only five dykes 

 could be found after a careful exploration of the whole 

 occurrence, and they were of insignificant dimensions. 

 But very few dykes also occur at Beloeil mountain. A 

 large number of the dyke rocks have been collected from 

 the various occurrences and are now awaiting investiga- 

 tion in the geological department at McGill University. 

 The work on the dykes of Mount Royal is now well ad- 

 vanced and, it is hoped, will be ready for publication 

 shortly. They form a most remarkable series, comprising 

 bostonites, tinguaites, solvsbergites, camptonites, four- 

 chites, monchiquites, and alnoites. Most, if not all, of the 

 types of dyke rocks which have been described as occur- 

 ring in association with the alkaline rich magmas of the 

 theralite and nepheline-syenite groups in any part of 

 the world are thus represented. To these dyke rocks 

 belong Hunt's phonolite, which he considered to differ 

 from the trachyte in that it contained a certain portion of 

 natrolite. The two occurrences which he describes 1 are 

 both from points near Montreal. They are nepheline 

 bearing dykes in an advanced stage of alteration. 



As has been mentioned, dyke rocks which from their 

 composition are clearly connected with the intrusions 

 of the Monteregian hills have been found cutting the rocks 



1 Geology of Canada, pp. 659-61 



