2.10 Canadian Record of Science. 



of the plain at very considerable distances from any of the 

 main centers of activity. Thus, in addition to occurren- 

 ces of Laprairie, Lachine, Riviere des Prairies, Ste Anne 

 de Bellevue, St. Paul's Island in the vicinity of Montreal, 

 several dykes and flows of " trachyte " (bostonite) are 

 noted by Hunt and Logan as occurring about Chambly, 

 which is six miles to the south of the line of the 

 Monteregian hills, 1 while the occurrence of a "dolerite" 

 dyke at St. Hyacinth, ten miles north of the line is 

 mentioned. 2 



A sheet of trap evidently connected with these intrus- 

 ions also occurs at St. Lin, 3 twenty-four miles north of 

 this line, where it alters the Chazy limestone through 

 which it cuts into a pink marble. It is very much de- 

 composed, but evidently belongs to some variety of the 

 nepheline or melilite dyke rocks above mentioned. 4 



Whether the camptonite and in some cases bostonite 

 dykes, described by several authors from various points in 

 the states of Maine, New Hampshire and Vermont, 

 adjacent to the Canadian line, and still more distant occur- 

 rences of similar dyke rocks in the state of New York, 

 are connected with the Monteregian hills, is not yet 

 known. There seem to be no intrusions of nepheline- 

 syenite or essexite hitherto discovered with which these 

 southern dykes can be connected in the districts in which 

 they occur. The umptekite intrusion of Red Hill, Molton- 

 boro, N. H., is however, closely related to the Monteregian 

 pulaskite in character and composition, and may prove to 

 be such a center. 



STRUCTURE AND ORIGIN OF THE MONTE- 

 REGIAN HILLS. 



The question of the mutual relations and relative age 

 of the several rock types constituting these hills presents 

 many points of interest. In the case of Mount Royal the 



1 Geology of Canada, pp. 2C9 and 657. 2 Ibid., p. 210. 3 Ibid., p. 133. 



4 F. D. Adams, " Report of Geology of Laurentian Area to the North of Island of 

 Montreal," Ann. Rept. Geol. Surv. of Canada, Vol. VIII, J., p. 139. 1826. 



