346 LIETJT.-GEN". C. A. MCMAHOtf ON [May I9OO, 



cryptocrystalline mica in describing the gneissose granite of 

 the North-western Himalaya. These strings and patches are not 

 pleochroic, and give a very confused image in converging polarized 

 light. They are partly fibrous, and are fringed with fine needles 

 of what appears to be sillimanite, which radiate in all directions 

 from the sides and ends of the cryptocrystalline mica. The needles 

 exhibit straight extinction, a positive axis of depolarization, and 

 many of them have the cross-partings characteristic of sillimanite. 

 The occasional presence of this mineral in granite is well known. 1 

 The last-described specimen also contains microscopic crystals of 

 rutile, and some colourless mica which appears to be highly altered 

 and degraded biotite. 



(2) Astor to Ramghat. 



The rock prevalent between Astor and Hatu Pir is a continuation 

 of the acid variety of the Hatu Pir Granite, seen in force at 

 Nanga Parbat, but not sheared to the same extent as the latter. 

 It is foliated, however, and shows au gen-structure. It resembles 

 very closely some specimens of the gneissose granite of the North- 

 western Himalaya. 



My next specimen comes from the flank of Hatu Pir, and is the 

 normal and older variety of the Hatu Pir Granite already described 

 (p. 341). This specimen does not exhibit any parallelism of 

 structure. 1 have no field -observations regarding the relationship 

 of the acid to the normal variety of the granite at this point : that 

 will be shown later on. 



(3) Ramghat to Chilas. 



This traverse enables us to obtain another view of the rock- 

 succession seen between Astor and Ramghat. Leaving behind 

 the quartz-diorite of the Ramghat cliffs, described on a subsequent 

 page, the mountains along the left bank of the Indus as far as 

 Julipar, a distance of 20 miles, are composed of the Hatu Pir 

 Granite. The hand-specimens show more or less parallelism of 

 structure, but this is not observable under the microscope. The 

 quartz, however, is much broken up into tessellated grains, and 

 some of the felspars are fractured. 



The granite along this section is penetrated by dykes of greenish- 

 grey pyroxenite which has a specific gravity of 3*107. It is a 

 fine-grained noncrystalline mixture of dark hornblende and white 

 pyroxene, the latter being rather subordinate to the amphibole. 



The hornblende in this rock, which I shall speak of as the Lecher 

 Pyroxenite, is of a pale brownish-green in transmitted light. 

 It occurs in allotriomorphic grains and prisms, and in very thin slices 

 shows a single diallage-iike cleavage. Extinction from 12° to 17°. 

 The pleochroism is hardly apparent in thin, but is very definite in 

 thick slices. 



The pyroxene is in some respects a puzzling mineral. It is colourless, 



1 E. S. Dana, ' Text-Book of Mineralogy ' 2nd ed. (1898) p. 434. 



