206 On the Geology of the Island of Montreal. 



siderable numbers, (though commonly distinct) are spherical 

 knots of pink feldspar, nearly pure, minutely crystallized, and 

 filled with the acicular hornblende or augite of the general 

 mass. The feldspar, it will be observed, is here pink. I met 

 with a detached mass on the north side of the homogeneous 

 trap, traversed by a vein two inches thick, of red feldspar. 



Judging of the quantity of the trap met with, in the exca- 

 vation of the Lachine Canal, by what is thrown out, it is very 

 considerable. It is principally of the second, or compact 

 kind, and is massive ; rarely in veins, when it might be visi- 

 ble in the sides of the canal, as in fact it is, not far from the 

 bridge at the west end, and at about three miles from the 

 same end. The third form, when penetrating the limestone 

 in veins, effervesces slightly with acids, and even contains 

 well preserved terebratulce, covered with a ferruginous crust, 

 and surrounded by crystals of basaltic hornblende. 



The fourth form abounds most near the limestone, at the 

 sides of the eastern division of the hill, and on the higher parts 

 of the very rough northeast flank of Mount Trafalgar ; where 

 it graduates, in passing downwards, through the homogeneous 

 into the crystalline black form. It can, indeed, scarcely be 

 called a trap ; although forming part of the same deposition 

 with the other portions of the hill. It cannot be distinguished, 

 in carefully selected hand specimens, from the sienite of the 

 summit of Peek Island, in Lake Superior ; and with some 

 difficulty from an amphibolic granite, from near Rice River, 

 in the Lake of the Woods. It is a mixture, occasionally fine, 

 of white or transparent feldspar, white crystalline quartz, and 

 a little copper-coloured mica, often in nests. In this granite- 

 like rock, prisms of hornblende are scattered at random, 

 sometimes mere dots, or acicular ; but at others, one or more 

 inches long, and of corresponding breadth. As has been 

 mentioned above, this form, by an augmentation of its horn- 

 blende, passes into perfect trap, and, on the other hand, as 

 frequently, wholly loses the imbedded crystals in question. 



