LATEK DIKES 517 



general mass of the rock. The rock bears a resemblance to that of Saint 

 Flavien, of which it may be a continuation, and like it is highly cupriferous. 



So far as yet examined, some half dozen specimens, the diorite of the 

 above description proves to be a fine-grained diabase. The diabase forms 

 two bands crossing Saint Francis river here, one having a width of a 

 quarter of a mile and the other of about 50 feet. The distance between 

 them is rather more than a quarter of a mile and is occupied by very dark 

 graphite limestone and greenish gray sedimentary slates. What appears 

 to be devitrified glass was found along the contact of the diabase and the 

 latter rock. These rocks have been here mentioned under the head of 

 "Later dikes" because of their lithological similarity to known dikes and 

 the absence as yet of satisfactory proof that they are not themselves also 

 of that class. This entire series offers an excellent field for an interest- 

 ing and important detailed investigation. 



The Monteregian Hills 



This name, which has now gained general currency in geological nomen- 

 clature, was proposed by Dr F. D. Adams in 1903* to designate a series 

 of volcanic hills which crosses the Saint Lawrence valley in the south- 

 western part of the province of Quebec. These hills, which are eight in 

 number, are of volcanic origin, either stocks or laccolites. They owe their 

 present relief to differential erosion, and consequently are hills of the 

 butte type. 



Six of the eight hills form a nearly east and west line, standing about 

 10 miles apart. In order from west to east, they are mount Eoyal, at the 

 foot of which stands the city of Montreal (Mont Eoyal) ; Montarville 

 or Saint Bruno, Beloeil or Saint Hilaire, Eougemont, Yamaska, and 

 Shefford. The remaining stand at the south of this line, Brome being 

 2y 2 miles from Shefford and mount Johnson 6 miles from Eougemont. 



The lithological characters of these hills are such as to show them to 

 be a distinct petrographical province, and to bear little, if any, relation 

 to the rocks hitherto described in this article. In every hill there is a 

 large development of essexite, which frequently passes into theralite, and 

 in every one which has been studied in detail an alkali syenite, such as 

 nordmarkite, pulaskite,. or nepheline-syenite. Their general features 

 may be presented in the following summary form : 



Mount Eoyal has an area of about 2 square miles and attains an eleva- 

 tion 769.6 feet above mean sealevel. The altitude of the Grand Trunk 



* Journal of Geology, volume xi, no. 3. "The Montereglan hills, a Canadian petro- 

 graphlc province." 



