The Monteregian Hills. 239 



intermediate between the essexite and the pulaskite, 

 occurring on either side of it, thus representing an 

 intermediate zone in which the differentation was not 

 quite completed. It is, however, much more nearly 

 allied to the essexite, being alkalicalcic and dosodic, and 

 although in the absence of a complete analysis or detailed 

 measurements its position in the new classificatian cannot 

 be determined with absolute certainty, there is very little 

 doubt that it also, like the. essexite adjacent to it, is an 

 andose. 



Dykes. — A feature in connection with Mount John- 

 son, and one possibly connected with its somewhat peculiar 

 structure, is the almost entire absence of dykes. These 

 were found only in two places, and in both cases the 

 dykes were small in size. The first of these localities is 

 on the northeastern margin of the intrusion, where the 

 dyke occurs in association with and probably cutting the 

 hornstone. It was found as large angular blocks in the 

 heavy maple bush which here covers the slope of the 

 mountain, but is undoubtedly in place in the immediate 

 vicinity. The rock is very dark gray in color and very 

 fine in grain, and belongs to the camptonites. It has a 

 porphyritic structure, the very numerous phenocrysts 

 consisting of hornblende and pyroxene. The hornblende 

 phenocrysts are deep-brown in color and strongly pleo- 

 chroic, the mineral being the same basaltic hornblende 

 described in the essexite. The pyroxene of the pheno- 

 crysts is pale purplish in color and shows a marked dis- 

 persion of the bisectrices. Both minerals have very 

 perfect crystalline forms. The plagioclase of the rock is 

 very basic in character, as shown by its high extension. 

 The rock resembles very closely certain occurrences found 

 on . Monnt Eoyal. The size of this dyke is not known, 

 but it probably has not a width of more than a foot or two. 

 The other dykes occur on the southeastern slope of the 

 mountain by the side of the road leading down from the 

 quarries here. At this locality there are four small 



