56 i Bejwrts and Proceedings — 



a whitish rock, more like the marble in a very crushed condition 

 than a Jurassic limestone ; next comes indubitable Jurassic lime- 

 stone, and lastly gneiss. In one place the top of the lower mass 

 of marble could be seen within a few inches of dark shaky Jurassic 

 rock. On the eastern side of the Pass two small pits had been 

 opened since the author's last visit ; they also showed the top of 

 the marble underneath the Jurassic rock. Both rocks were rather 

 shattered near the junction, but were as different as they well could 

 be. The one resembles the marble, associated elsewhere in the 

 Alps with crystalline schists; the other, a member of the Jurassic 

 system. There is not the slightest sign of a passage between them, 

 but much to suggest faulting. The field evidence is confirmed by 

 study, macroscopic and microscopic, of the specimens. Accordingly 

 the author adheres to the view already expressed, that the white 

 marble is a rock much older than the Mesozoic era. 



2. "Geological and Petrographical Studies of the Sudbury Nickel 

 District (Canada)." By T. L. Walker, Ph.D., M.A. (Communicated 

 by J. J. H. Teall, Esq., M.A., F.R.S., Sec.G.S.) 



Sudbury is a small town situated in Northern Ontario, in the 

 centre of the nickel-mining district. North of the Great Lakes 

 granite and gneiss form almost boundless terranes, interrupted only 

 by belts of Huronian rocks, which are in turn associated with post- 

 Huronian eruptives, the most important of which are the large 

 nickel-bearing massives. 



The Huronian rocks in the vicinity of Sudbury were examined by 

 Professor Bonney, who published his results in the Quarterly 

 Journal of this Society (vol. xliv, 1888). These rocks form a large 

 belt extending from the northern shore of Lake Huron north- 

 eastward for several hundred miles. In the immediate vicinity of 

 Sudbury they are composed of quartzite, mica-schist, phyllite, slate, 

 volcanic breccia, and greywacke. 



Far more interesting are the nickel-beai'ing rocks, which are 

 eruptive and form long elliptical stocks which conform to the strike 

 of the Huronian rocks containing them. Contact-action indicates 

 that they are younger than the rocks previously referred to. The 

 smaller eruptives are composed of greenstone, which appears to have 

 been formed from norite or gabbro. Some of the larger eruptives, 

 however, have been highly differentiated on cooling, as they are now 

 composed of granite and greenstone with gradual transitions from 

 the one to the other. The greenstone generally forms one side of 

 the eruptive, and on the outer border is often characterized by large 

 masses of nickeliferous pyrrhotite, chalcopyrite, and nickeliferous 

 pyrite, with frequent smaller masses of magnetic iron-ore rich in 

 titanic acid. The writer regards these mineral masses as genetically 

 related to the greenstone and granite, in that the}' appear to be the 

 extreme products of differentiation. About half the world's nickel 

 supply is drawn from these deposits. 



The greenstone is generally somewhat altered, but at times it is 

 only slightly changed, when it is seen to be typical norite. 



The alteration of augite and hyperstheue is described in detail, 



