244 THE CANADIAN NATURALIST. [Vol. ix. 



that when the rock is pulverised the magnet removes almost 

 nothing;. The specific gravity of different fragments of the rock 

 varied from 2-927 to 3-005. An analysis was made some time 

 ago, and, as the composition appeared unusual, search was made 

 for descriptions of similar rocks from other localities, but none 

 could be found. Since then, however, Mr. G. W. Hawes has 

 described rocks of wonderful similarity from Campton, in the 

 State of New Hampshire.''" An analysis, by Mr. Hawes, of one 

 of these diorites is given under 11. for comparison with I., which 

 is an analysis of the diorite from Montreal just described : — 



I. II. 



Silica 40-95 41-94 



Alumina lG-45 15-36 



Ferric oxide f 1 3-47 S-21 



Ferrous oxide 9-89 



Manganous oxide 0.33$ 0.25 



Titanium dioxide 3.39 4.15 



Lime 10.53 9.47 



Magnesia G.l 5.01 



Potash : 1.28 0.19 



Soda 4.00 5.15 



Phosphoric Acid 0.29 



Carbon dioxide ... 2.47 



Loss on ignition 3.84 3.29§ 



100.63 100.44 



On boiling T. with "hydrochloric acid for several hours, and 

 filtering, the insoluble residue after ignition amounted to only 

 51.80 per cent. Although the amount of carbon dioxide was 

 not determined, it must constitute a large proportion of the loss 

 which the rock sustains on ignition ; for acetic acid dissolves 4.02 

 per cent, of lime and 0.67 of ferrous oxide, and these bases, if 

 calculated as carbonates, would require 3.57 per cent, of carbon 

 dioxide. The basic character of the rock, and the extent to 

 which it is dissolved by hydrochloric acid, seem to indicate a 

 feldspar of the nature of anorthite. In that case a considerable 

 proportion of the alkalies must belong to the hornblende ; but 



* Geology of New Hampshire, Part IV, p. 160. Americayi Journal oj 

 Science. 1879, p. 148. 



I All the iron is calculated as ferric oxide, the ferrous oxide not 

 having been determined. 



X With a little cobalt. § Water. 



