476 Prof. T. G. Bouncy and Miss C. A. Raisin. 



colourless, the other brown, in little films, all scattered in a fairly 

 glass-clear ground-mass ; one or two grains of iron oxide and possibly 

 of rntile occur. The crystals generally have a foliated arrangement, and 

 are somewhat irregularly grouped, comparatively free lacunae occur- 

 ring here and there. The garnets are clear, and contain a few enclo- 

 sures (? cavities) ; they usually occur in well-formed dodecahedra, and 

 are about 0'002 inch in diameter. This is seldom and very slightly 

 exceeded, but much smaller specimens are not rare. The white mica 

 is less abundant where the garnets are common, and has a tendency 

 to occur in lai-ger crystals and group itself round the lacunae. With 

 crossed nicols the greater part of the ground-mass exhibits a rather 

 minute mosaic structure, and is probably, at least to a considerable 

 extent, secondary felspar. The larger interspaces prove to be in some 

 cases aggregated granules of quartz, in others an almost water-clear 

 felspar, cleavage planes and occasional twinning being perceptible 

 The outline of the felspar is very irregular, and it is associated some- 

 times with granules like those above mentioned, as though it had 

 been partly replaced by them. There can be no doubt that the pied- 

 montite, the garnet, and possibly some of the white mica are of 

 secondary origin. It is even doubtful whether all the larger grains 

 of felspar and quartz are intact, for some contain more microliths 

 than might have been anticipated. Calcite occurs locally in patches ; 

 in one place also a slightly granular mineral, giving bright tints with 

 crossed nicols. The rock is now a piedmontite schist, but it is diffi- 

 cult to suggest what its original condition may have been, not improb- 

 ably a fairly coarse-grained gneissoid or granitoid rock. 



Another specimen from the left half of the Gargo glacier bears 

 some resemblance to the preceding, but is less micaceous and paler 

 in colour ; also it contains a vein of quartz with some minute calcite. 

 Even on microscopic examination the distinctions for the most part 

 are only varietal, but broken felspars of considerable size are rather 

 more conspicuous in 'the specimen, and the rock generally affords 

 very marked indications of fracture and reconstitution. There is 

 another specimen from the left aide or moraine of the Gargo glacier 

 (below the icefall), which has a general resemblance to the last but 

 one, but has a slightly more slabby character. 



These rocks have been compared with a specimen of the pied- 

 montite schist of Japan, presented to one of us by the kindness of 

 Professor Koto. This contains the characteristic mineral about as 

 abundantly arid as well developed as the Gargo specimens, but has 

 more iron-glance (?), and more white mica, which sometimes seems 

 to be slightly tinted by the manganese. The rock also is more defi- 

 nitely foliated. 



Schist with Conspicuous Secondary Mica. From Dasskaram Needle 

 comes a pale grey, closely laminated silvery schist, markedly cal- 



