272 FRANK D. ADAMS 



line in the essexite and which is, as has been mentioned, either 

 kaolin or muscovite. Probably both are present. 



Apatite is present in considerable amount and in the form of 

 perfect crystals, occurring chiefly in the mica, hornblende, and 

 sphene. 



The iro7i ore and sphene present the same characters as in the 

 case of the essexite, but the latter mineral is relatively more 

 abundant than in that rock. 



An analysis of this pulaskite is given in the accompanying 

 table together with analysis of the pulaskite and the nord- 

 markite of Shefford mountain described by Dresser. Analysis 

 of three allied rocks from other localities are added for pur- 

 poses of comparison. 



^\\& mode oi the Mount Johnson pulaskite (No. VII), calcu- 

 lated from the analysis given above, is as follows: 



99.68 



This proportion of the various minerals expresses exactly the 

 chemical composition of the rock as presented by the analysis, 

 except that a very small excess of silica, amounting to 0.06 per 

 cent., is required. 



The calculation shows clearly the fact, ascertained by the 

 study of the thin sections of the rock, that a considerable per- 

 centage of sphene is present, a mineral which does not occur at 

 all in the essexite. 



The anorthite is probably in combination with the other 

 feldspathic constituents in the form of anorthoclase. The calcu- 



