260 ROYAL SOCIETY OF CANADA 



up through the limestone, a large block of the limestone on the north 

 side of the hill being tilted by the intrusive breccia till it is now stand- 

 ing at an angle of 30°. The breccia has an igneous cement and has had 

 two stages of development. The fii'st intrusion, enclosing very numerous 

 fragments, was at least partly solidified when it was fissured and more 

 molten matter extruded. A dyke on top of the hill shows unmixed igne- 

 ous material in the middle, but with increasing numerous inclusions to- 

 wards the sides, finally passing into the breccia where fragments occur 

 in much larger amount than paste. 



To the northeast of the hill there is a nearly equal area in a level 

 field, with numerous large blocks of breccia, up to six feet across, which 

 do not seem to have travelled far. These blocks are confined so definitely 

 to a limited area that it would suggest an extension of the main occur- 

 rence. This suggestion is, however, not confirmed by any topographic 

 feature such as a hill, — so striking in the first instance. 



The fragments in the breccia are mostly angular, though a great 

 many are rounded. These latter have probably had the comers flused o3 

 by the molten matter. The commonest inclusions are homstone — derived 

 from a baked shale, and sandstone, — probably from the Potsdam. Be- 

 sides these there are, limestone, — altered to marble, biotite-granite, 

 pyroxenite, several fragments of crystalline quartz, and a hornblende rock. 

 The granite fragments are the most altered, being much chloritised and 

 showing a green colour. Many pieces of the sandstone show the action 

 of the heat which has produced a zone of quartzite. Pyroxenites and 

 hornblende rocks are well known difierentiation products of the main 

 mass of the Monteregian intrusives. Their presence here shows the oc- 

 currence of these rocks near the source of the breccia. 



The paste of the breccia contains numerous large phenocrysts of 

 pyroxene frequently an inch across. There are also a few phenocrysts 

 of biotite up to one half-inch, while small fiakes are to be found all 

 through the mass. The matrix is of a greenish gray colour, weathering 

 to an intense rusty brown. The dyke material does not become rusty. 



"Wlien examined in thin section, the paste of the breccia, although 

 much decomposed in most slides, yet gives a great deal of information. 

 It undoubtedly consists of igneous material, — apparently alnoite. It 

 shows pyroxene, biotite, olivine, perovskite, melilite, and probably hydro- 

 nephelite. The pyroxene is in two varieties, — augite with extinction up 

 to 45°, and a pale variety about 30°, both occurring as phenocrysts, of 

 which only residues are now to be seen in the slides examined. The very 

 large phenocrysts mentioned above were found to be of this variety. The 

 biotite is very abundant all through the slides. It is found to be well 

 preserved in small, freely-developed phenocrysts of a pale reddish-brown 



