70 THE ROYAL SOCIETY OF CANADA 



large offshoots running away from the hill on the north side. Several 

 dykes of a camptonite-like rock cut these outliers where they cross 

 the highway . . ." 



Megascopically, the rock presents considerable variation. In 

 the centre the rock is composed of phenocrysts of augite, olivine, and 

 biotite in a dark grey grbundmass. The augite occurs in large indi- 

 viduals up to half an inch in diameter, and is black in colour. Pale 

 green olivine is found in huge phenocrysts commonly an inch across, 

 and biotite occurs in large irregular crystals, up to half an inch in 

 diameter. 



In the groundmass itself there are a large number of small white 

 grains, commonly a couple of millimetres in diameter; these appear 

 to be largely composed of calcite, but in many cases have a dark 

 centre of augite or olivine. They appear to be the remains of small 

 olivine and augite crystals which have been partially resorbed and 

 although it is not so noticeable in the larger individuals, close examina- 

 tion shows the same resorption about the border. 



Harvie found the rock to consist of phenocrysts of augite and 

 olivine, two generations of biotite, labradorite, two generations of 

 apatite, ilmenite, pyrite and pyrrhotite, perovskite, a zeolite con- 

 sidered to be natrolite and a base of nepheline as well as two unknown 

 minerals. Of these the former was "at first taken for apatite. ... It 

 has the same low refraction, dull polarization and colour, but is 

 monoclinic, with an extinction up to 43°. A second unknown mineral 

 also occurs in small amount, being well preserved as short prisms 

 with good outlines, showing slight cleavage, and having an inclined 

 extinction up to 45°. It has a refraction distinctly higher than that 

 of calcite and polarizes in dull to pale yellow tints." 



These minerals were not all found by the writer but it must be 

 pointed out that the Monteregian outliers described in this paper 

 are all of very variable composition, and it is quite probable that 

 sections from other parts of the same outcrops would in many cases 

 show different mineralogical compositions from those described. 

 This outlier at La Trappe does indeed present several different facies 

 whose relationships with one another are masked by a heavy blanket 

 of drift, so that no division into a principal phase and subordinate 

 variations can be made. The writer will content himself simply with 

 describing what he considers to be the most characteristic type 

 present, together with some facies which appear to be transitional 

 between this type and the breccias, and which are represented by 

 several dykes and outliers in the neighbourhood. It must, however, 



