324 THE CANADIAN NATURALIST. [Vol. viiL 



DESCRIPTION OF PLATE III. 



Fig. 1. Diabase from Grenville, lot 9, range IV, showing augite 

 plagioclase, magnetite and viridite (magnified 28 diam- 

 eters). 



Fig. 2. Dolerite (Feldspar Basalt) from River St. Simon, showing 

 augite, plagioclase, magnetite and a little viridite. The 

 cruciform group in the right hand upper corner is plagio- 

 clase. (x 78). 



Fig. 3. Dolerite from River Gagnon, showing augite (a twin on the 

 left) plagioclase and magnetite, (x 14). 



Fig. 4. Diorite from Madoc, Ontario, showing bluish-green horn- 

 blende, plagioclase, magnetite, and pyrite (the square 

 crystal in the lower right hand corner), (x 78). 



Fig. 5. Apatite in rock from Grenville, lot 4, range VI. The portion 

 of the drawing shaded black, excepting the spots in the 

 apatite crystals, consists of magnetite and pyrite, chiefly 

 the latter, (x 78) 



Fig. 6. (a). Cross section of apatite crystal with numerous cavities 

 a few of which show bubbles, and are perhaps liquid 

 cavities. (6). Cross section of apatite crystal, showing 

 the black bodies referred to in the text. (c). Longitudinal 

 section of rounded apatite crystal with black bodies sim- 

 ilar to those in b. (All x 78.) 



