4 SIDNEY POWERS 



descended can only be estimated as probably several thousand 

 feet.^ 



{B) Some inclusions have sunk. — ■ 



Montreal, Canada: A number of breccia dikes have been 

 described from the vicinity of Montreal and the Monteregian Hills 

 by Robert Harvie.^ The dikes will be mentioned in the order in 

 which they are described by Harvie. 



Near La Trappe in the Oka Mountains are two inclusion- 

 bearing alnoite dikes, one of which is enlarged to a width of i8o 

 feet, while the other is 25 feet wide and traceable for half a mile. 

 The fragments are of Grenville limestone, Laurentian gneiss, Pots- 

 dam sandstone, and Beekmantown sandstone. The last two 

 formations are stratigraphically higher than the exposure which 

 is near the contact of the Grenville and Laurentian. Therefore 

 some of the blocks rose, others sank. 



Near Ste. Anne de Bellevue is a dike a foot wide cutting Trenton 

 limestone and containing angular fragments of sandstone, horn- 

 stone, and limestone. The sandstone has a quartzitic rim, the 

 hornstone was apparently originally a shale, and the limestone is 

 changed to a crystalKne marble. 



On Westmount Mountain at Little's quarry is a large breccia 

 camptonite dike about 4 feet wide. In one side of the dike an off- 

 shoot from it "has eroded or stoped out and filled a large cavity." 

 The heat of the intrusive has baked the hmestone, and a section from 

 the unaltered limestone to the dike shows increasing baking and 

 shattering until the blocks of hmestone drop off into the dike-rock, 

 where they form the bulk of the angular inclusions. Harvie says: 



In this process of shattering by which the action of stoping went forward 

 every gradation is visible, from the solid unaltered limestone to the fragments 

 finally frayed off and held in suspension in the breccia. The circulation of the 

 materials of the intrusive has evidently been very vigorous, since fragments of 

 other rocks, granites, etc., are found carried up to the top of the stope within 

 a foot of the unshattered limestone. The magma has not exerted any pro- 



I The writer is indebted to Professor C. H. Warren, of Boston, for the information 

 concerning the inclusions in this dike. 



^ On the origin and relations of the Paleozoic breccia in the vicinity of Montreal, 

 see Trans. Roy. Soc. Canada, 3d ser., Ill (1909), 249-78. 



