60 THE ROYAL SOCIETY OF CANADA 



Eastern Exposure, Como, Que. — At the sign post, one mile east of 

 Como Station, the railway cuts through a hill strewn with more or 

 less rounded blocks of alnoite No outcrops that could be definitely 

 assumed to be in situ were found, but from the character of the hill, 

 and from the absence of boulders in all parts of the surrounding area, 

 it was assumed that this is another occurrence of alnoite similar to 

 that half a mile to the west and also at Isle Cadieux. 



The rock in the hand specimen is very similar to the non-porphy- 

 ritic varieties at Isle Cadieux and Como, and consists of a dark grey, 

 fine-grained rock in which the only mineral that can be distinguished 

 is biotite which occurs in tiny grains up to 2 mm. in diameter. 



Under the microscope the rock also resembles the neighbouring 

 alnoites and consists of grains of augite, bleached and partially re- 

 sorbed biotite, and chrysolite, which has been partially replaced by 

 monticellite; there are also grains of monticellite in a groundmass of 

 melilite and carbonates with black iron ore and perovskite as acces- 

 sory constituents. The chief difference between this rock and those 

 described above, and from Isle Cadieux, lies in the fact that the bio- 

 tite is much fresher than at these other localities. Chrysolite is 

 more abundant than augite, and monticellite is present both as re- 

 sorption rims about the chrysolite and also as small hypidiomorphic 

 grains. 



Melilite, perovskite, apatite, and iron ore are present in about 

 the same proportions as at Como. 



