472 Prof. T. G. Bonney and Miss C. A. Raisin. 



ments must have occarred long anterior to those which have pro- 

 duced the existing chain. Lastly, two partially altered sedimentary 

 rocks are of some interest. The first, from a fallen fragment half- 

 way between Samaiyar village and Strawberry Camp, on the left 

 bank of the valley, is a blackish, compact, slightly-cleaved rock, not 

 distinctly crystalline, in which are scattered several crystalline 

 grains, the largest slightly more than one-eighth of an inch in 

 diameter. This has one fairly well-marked cleavage, with a sub- 

 vitreous, slightly oily lustre, and a second more imperfect, meeting it 

 at an obtuse angle. The hardness seems to be slightly less than 5. 

 Under the microscope the ground-mass is seen to consist of minute 

 films of a sericitic mica mixed with a minute colourless mineral and 

 granules of opacite and ferrite. In this are scattered larger irregular 

 grains and plates of a black mineral, with raggedly outlined flakes 

 of biotite, containing much of the ground-mass, some prisms (prob- 

 ably rutile), and two or three specimens of a larger mineral (probably 

 the same species as that already mentioned). The best defined has 

 two cleavages, one more strongly developed than the other, meeting 

 at an angle of about 76, and extinction takes place at an angle of 

 30, or a little less, with the former. The crystals exhibit a rather 

 irregularly outlined prismatic form, the sides being roughly parallel 

 with these cleavages, and are crowded with minute materials, appa- 

 rently identical with the ground-mass. This presents a slight 

 resemblance to that of the ottrelite rock of the Forges de la Commune, 

 Ardennes, and of one or two schistose rocks from the Alps, which do 

 not belong to the most ancient group. Both the biotite and the above- 

 named mineral appear to have been formed in situ at a time when 

 molecular movements were not easy. We are unable to identify the 

 latter with any mineral known to us, but it somewhat recalls to 

 mind the " knoten and prismen " from certain Jurassic rocks in the 

 Lepontine Alps,* and even the couseranite from Vicdessos (Pyrenees). 

 If, does not seem to be tetragonal. We venture to suggest that it is 

 a hydrous alumina-lime-silicate allied to the scapolite group. The 

 matrix around the crystals is slightly coarser than elsewhere. Possi- 

 bly the peculiarities in this rock may be the result of contact meta- 

 morphism. The other rock from near Trough Camp, on the right 

 side of the neve, obviously contains rather angular fragments of 

 white marble imbedded in a hard matrix, grey, speckled with dark 

 green, in colour. The larger marble fragments are stained externally 

 with limonite ; many of the smaller are altogether brown. Micro- 

 scopic examination shows these to consist alike of crystalline calcite, 

 fairly coarse in the whiter parts, fine-grained in the iron-stained. 

 Both structures are sometimes present in the same fragment, and 

 their relations suggest that the fine-grained one comes from a 



* T. G. Bonney, ' Quart. JL Oeol, Soc.,' 1890, vol. 46, pp. 213221, 232-236. 



