282 FRANK D. ADAMS 



that the pipe would have in time been cleared of the earlier 

 pulaskite magma. 



The interesting question of the succession of the eruption of 

 the several magmas in this petrographical province, as well as 

 the causes of their differentiation, can be more profitably dis- 

 cussed when the other centers of eruption have been more 

 thoroughly studied. It is interesting to note the cumulative 

 evidence in favor of differentiation as an explanation of the 

 origin of these and similar groups of rocks, arising not only from 

 the repeated association of the various members of the group 

 at many centers in a single area like that described in the 

 present paper, but also at centers widely separated from one 

 another in different parts of the world. The occurrences 

 described by Ramsay ^ in the Kola peninsula may be especially 

 noted in this connection as closely allied to those of the Mon- 

 teregian hills, a soda -syenite (umptekite) occurring about the 

 margin of an intrusion of the nepheline-syenite which constitutes 

 the massive, while theralite is also found as a differentiation 

 product of the same intrusion. 



The author desires to acknowledge his indebtedness in con- 

 nection with this investigation to Miss Rosalind Watson, of 

 Victoria, B. C, who, when a student at this university began the 

 study of Mount Johnson; also to Professor Rosenbusch, Professor 

 Iddings, and Professor C. H. McLeod for valuable aid during 

 the course of the work. 



Frank D. Adams. 



McGiLL University, 

 Montreal. 



^Das Nepkelinsyeniigebiet auf der Halbuisel Kola. Fennia II, No. 2. Helsing- 

 fors, 1894. 



