2 50 FRANK D. ADAMS 



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 proportion of natrolite. The two 

 occurrences which he describes ^ are both from points near Mon- 

 treal. They are nepheline bearing dykes in an advanced stage 

 of alteration. 



As has been mentioned, dyke rocks which from their com- 

 position are clearly connected with the intrusions of the Monte- 

 regian hills have been found cutting the rocks of the plain at very 

 considerable distances from any of the main centers of activity. 

 Thus, in addition to occurrences at 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, ^ while the occurrence of a "dolerite " dyke at St. Hyacinth, 

 ten miles north of the line, is mentioned. ^ 



A sheet of trap evidently connected with these intrusions also 

 occurs at St. Lin, ^ twenty-four miles north of this line, where it 

 alters the Chazy limestones through which it cuts into a pink 

 marble. It is very much decomposed, but evidently belongs 

 to some variety of the nepheline or melilite dyke rocks above 

 mentioned. 5 



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 the still more distant occurrences 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- 



' Geology of Canada, pp. 659-61. 3 Ibid., p. 210. 



^ Ibid., pp. 209 and 657. "* Ibid., p. 133. 



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

 Montreal," Ann. Rept. Geol. Surv. of Canada, Vol. VIII, J, p. 139, 1896. 



