The Monteregian Hills. 225 



ore. It also occurs in the sphene as well as in the iron- 

 magnesia constituents, in the nepheline, and also, although 

 much less frequently, in the feldspar. Its large amount 

 is shown by the high percentage of phosphoric acid in the 

 analysis of the rock, 1.23 per cent. Another specimen of 

 the rock in which the phosphoric acid was determined by 

 Dr. B. J. Harrington gave 1.01 per cent. These figures 

 represent 2.79 per cent, and 2.35 per cent, of apatite, re- 

 spectively. It is usually somewhat turbid from the 

 presence of minute dust-like inclusions. 



Magnetite occurs chiefly inclosed in the iron-magnesia 

 constituents, but is occasionally found in the feldspar. It 

 is black, opaque, and highly magnetic, and is usually 

 allotriomorphic, but occasionally presents an approxima- 

 tion to definite crystalline outline. As shown by the cal- 

 culation of the analysis of the rock, this iron ore contains 

 a considerable percentage of titanic acid. 



Sphene is not found in more than one-half of the speci- 

 mens examined. When present it is not very abundant 

 and usually occurs as well-defined wedge-shaped crystals, 

 often of considerable size. 



In the accompanying table analyses are given of the 

 normal essexite which forms the greater part of Mount 

 Johnson, and of the finer-grained olivine-bearing variety 

 of the same rock found at the summit of the mountain. 

 For purposes uf comparison there is presented in the same 

 stable the analysis of the essexite from Shefford mountain, 

 which belongs to the same Monteregian province, together 

 with analyses of the original essexite from Salem, Mass., 

 and of allied rocks from two other localities. A partial 

 analysis of the transitional rock between the essexite and 

 the pulaskite of Mount Johnson is also given. For the 

 analysis of the Mount Johnson essexite (No. 1) as well as 

 for that of the associated pulaskite, which is given below, 

 I am indebted to Professor Norton-Evans, while the 

 analysis of the olivine-bearing variety of the essexite 

 (No. 2) was made for me by Mr. M. F. Connor. The 



