548 Prof. Bonney — Rock-specimens from the Canadian Rocldes, 



altered oolites. Dr. Collie brought back a fragment (loose) with 

 a similar structure from the district considerably farther north. 

 From the foot of these mountains Emerald Pass leads eastwards to 

 Emerald Lake. The rock from its summit [2024] is a pale grey, 

 very compact limestone, like one of the purest English Carboniferous 

 limestones, with rhomboidal jointing, weathering buff colour, and 

 developing a fine, slightly wavy banding. The structure, on micro- 

 scopic examination, proves to be due to coarser and finer grains of 

 calcite, slightly dolomitic. Two or three irregularly outlined, larger 

 grains are suggestive of an organic origin. Other scattered specks and 

 grains occur, the latter hematite. Mount McNicoll is near Emerald 

 Pass, and its summit [2027] is 'a greyish limestone, which, from its 

 brown weathering, must contain a fair amount of iron. It has 

 a rather earthy odour and efi'ervesces, but not very briskly, with 

 HCl, and is probably not very pure. The rock [2028] from the 

 summit of the pass between it and Mount Shaughnessey is not quite 

 so ferruginous as the last, but otherwise is in all respects similar. 

 The summit of Michael's Mount [2029], part of the same massif, 

 is a cream-grey subcrystalline limestone, with faint rust-brown 

 spots and a few irregular patches of a darker grey colour. The 

 structure proves on microscopic examination to be rather irregular. 

 Grains of calcite, occasionally dolomitic, differing considerably in 

 size and arrangement, predominate ; the larger sometimes forming 

 little clusters with a pale-brown staining, which vary from rather 

 irregular to oval in outline, and sometimes grouped in a way sug- 

 gestive of the former presence of fragments of shells, etc. Kather 

 Irregularly distributed among this, and sometimes aggregated, are 

 small grains of a clear silicate, a few of which are partly idiomorphic 

 and exhibit twinning, Carlsbad or oscillatory. Probably they are 

 a secondary felspar, and a few dark specks are iron-oxide. 



Nearer to Mount Collie, on the north side of the Upper Yoho 

 Valley, are the following peaks: Mount Pollinger [2025], Mount 

 Kaufmann [2026], Insulated Peak [2030], and Yoho Peak [2032]. 

 The summit of the first is a pale-grey subcrystalline limestone, with 

 some resemblance to one of the dolomitic limestones of the Alps, 

 but becoming browner on weathered surfaces. Mount Kaufmann is 

 a grey limestone, showing thin bands differing in texture from the 

 rest, and projecting slightly from weathered surfaces. Insulated Peak 

 is a subcrystalline limestone of a grey colour, slightly streaked with 

 white, and showing faint traces of small spots, which weather 

 brown. Under the microscope it is found to consist of grains 

 (a large number being about double the size of the others), more or 

 less dolomitic, of a faint brown colour, with a slight pleochroism 

 in which, as a matrix, are occasional irregular stain-like spots of 

 a dirty brown colour (? bituminous). There are also a few minute 

 interstitial granules of a water-clear silicate, and the rock more 

 nearly than usual appi'oaches to a marble. Yoho Peak is a grey 

 subcrystalline limestone, assuming a buff tint on weathered surfaces 

 and veined with calcite. The summit of Trolltinderne, a mountain 

 on the eastern side of the Yoho Valley and just west of the water- 



