226 



Canadian Record of Science. 



methods recommended by Hillebrand and employed in 

 the very accurate, analytical work carried out in the 

 laboratory of the United States Geological Survey were 

 followed by both analysts, and every precaution was 

 taken to insure accuracy. 





I 



II 



48.69 

 2.71 

 17.91 

 3.09 

 6.41 

 0.05 

 0.15 

 3 06 

 7.30 

 0.08 

 5.95 

 2.56 

 1.11 

 not det. 

 0.95 



III 



53.15 

 1.52 



17.64 

 3.10 

 4.65 

 not det. 

 0.46 

 2.94 

 5.66 

 0.13 

 5.00 

 3.10 

 0.65 

 0.07 

 1.10 



IV 



V 



47.67 



18.22 



3.65 

 3.85 



0.28 

 6 35 

 8.03 



4.93 



2.97 



3.82 



VI 



Si0 2 



Ti0 2 



A1 2 3 ....... 



Fe 2 3 



FeO 



NiO + CoO ... 

 MnO 



48.85 

 2 47 



IP. 38 

 4.29 

 4.94 

 not det. 

 0.19 

 2.00 

 7.98 



5.44 

 1.91 

 1.23 



not det. 

 0.68 



46.99 



2.92 



17.94 



2.56 



7.56 



not det. 



trace 

 . 3.22 

 7.85 

 none 

 6.35 

 2.62 

 0.94 



6.65 



50.40 

 1.17 



| 5.58 



not det. 

 0.77 



MgO 



CaO 



6.77 



BaO 





Na„0 



K 2 



P 2 6 



CI . . 



H,0 



6.24 

 2.56 

 0.09 







Total .... 



99.36 



100.02 



99.84 



99.60 



100.15 





I. Normal essexite (andose), Mount Johnson, Quebec. 



II. Olivine-bearing essexite (essexose), Mount Johnson, Quebec. 



III. Essexite (akerose), Shefford mountain, Quebec, (American 

 Geologist, 1901, p. 201), (with CO 2 0.39 and SO 8 0.28). 



IV. Essexite (essexose), Salem Neck, Salem, Mass. (Washington, 

 Jour. Geol., 1899, p. 57). 



V. Theralite, Elbow Creek, Crazy Mountains, Montana. 



VI. Rock forming transition from essexite to pulaskite, Mount 

 Johnson, Quebec. (Partial analysis. The iron present is all calculated 

 as FeO.) 



The analyses (Nos. L and 2) of the two varieties of the 

 essexite from Mount Johnson can be readily calculated 

 out so as to show the quantitative mineralogical composi- 

 tion of the rocks. 



The calculation of the mode 1 — or relative proportion of 

 the minerals actually present gives the following result : 



1 Quantitative Classification of Igneous Bocks (C.I. P. W.) (University 

 of Chicago Press, 1903), p. 147. 



