278 ROYAL SOCIETY OF CANADA 



their own accord to the level of Utica, or in the surgings or periods of 

 rise and fall of the intrusive, such as are to be seen in volcanoes today, 

 one of these retreats carried the blocks to the lower level. 



The presence of these inclusions in the breccia proves that the in- 

 trusion must have taken place subsequent to the deposition of the forma- 

 tions represented. The breccia is therefore of Post-Oriskany age. As 

 mentioned before. Dresser has shown by another line of evidence that 

 the intrusion of Mount Shefford probably took place before late Carboni- 

 ferous times. Although this applies to one of the large and apparently 

 earlier main intrusives, nevertheless this conclusion is in a broad way 

 confirmatory of the conclusion above stated concerning the age of the 

 breccia. 



In the alnoite breccia on He Bizard numerous similar fragments 

 were found, one of which was examined in thin section and found to be 

 a pyroxenite. This rock is frequently found as a differentiation product 

 of the essexite intrusion and its presence as an inclusion indicates that 

 the alnoite is later than the essexite. Similarly the nepheline aplite con- 

 tains quite a few inclusions of a pyroxene hornblende rock which also is 

 a differentiation product of the essexite. 



It may be of interest to note that alnoite is of rare occurrence. Be- 

 sides the original locality at Alno, in Sweden, and the occurrences de- 

 scribed in this paper, other occurrences are known, — at Manheim, N.Y., 

 described by C. H. Smyth, Jr., and an alnoite-like rock near Ashcroft, 

 B.C., described by Terrier. In the district of Montreal, three occur- 

 rences were known before — at Ste. Anne de Bellevue,i at Point St. 

 Charles, on the island of Montreal, two miles south of Ste. Helen's 

 Island,^ and an alnoite-like rock near St. Lin, twenty-five miles north 

 of Montreal.^ 



MeaCanïiœ Library 



NEW YORK. 



IF. D. Adams, Am. Jour. Se, 3rd Series, Vol. XLIII, pp. 269-279, 1892. 

 2 J. A. Allan, unpublished. 



3 F. D. Adams, Geol. Survey, Canada, Ann. Rep., Vol. VIII, pt. .T.. n. 136 ; 

 also Rosenbusch, " Mikroskopishe Physiognaphie, Vol. II, p. 708. 



