Vol. 56.] THE GEOLOGY OF GILGIT. 355 



beds of slate, sometimes as much as 500 feet thick, are intercalated 

 with the limestone.' 



These limestones differ considerably in appearance, both in the 

 field and in hand-specimens, from those previously described. They 

 are compact in structure, pale bluish-grey, and weather cream- 

 colour. One that I analysed contained 57'09 per cent, of calcium 

 carbonate ; 42-65 of magnesium carbonate ; and '26 per cent, of 

 iron: it is, therefore, a dolomite. 



One of the specimens is a fine-grained breccia. Whether the 

 brecciation is due to dynamic causes, or represents detritus formed 

 at the foot of a coral-reef, I cannot say. Under the microscope the 

 specimens are finely granular in structure, and this fine granulation 

 is also seen in the fragments that make up the breccia. The 

 rhombohedral cleavage is well seen in all the specimens, but 

 twinning is rare. 



The specimen of the intercalated slate examined is a mylonite- 

 slate with a micaceous glaze on its surface. Under the microscope 

 the slice is seen to be composed of dark patches and streaks, in a 

 colourless groundmass consisting principally of fine grains of quartz, 

 often exhibiting micro-augen structure. The dark patches are com- 

 posed of magnetite, iron-pyrites, limonite, and carbon. The dark 

 colour of the rock is mainly due to the last-named substance. A few 

 grains of schorl and flakes of mica are scattered through the slice. 



The grey limestones end at Gircha, and are followed by slaty 

 schists yeined by granite as far as Misgah. At Misgah very fine- 

 grained micaceous grits come in. The grains are subangular, 

 and have not travelled far. They are composed mainly of quartz, but 

 fragments of triclinic felspar are also present. The mica is colour- 

 less, and looks like a secondary product resulting from the meta- 

 morphism of the interstitial mud. The slice contains a little schorl 

 and apatite, and numerous dots of ferric oxide. The grit seems 

 to have resulted from the erosion of some old granite. 



Between Misgah and the Kilik Pass the beds are vertical, and are 

 traversed by numerous dykes of granite. The samples sent me 

 prove to be the Baltit Hornblende- Granite. 



My last specimen from this section comes from the top of a peak, 

 18,000 feet high, at and above the Kilik Pass, looking down on the 

 Taghdumbash Pamir. It is a fine-grained slaty micaceous grit. 

 The matrix is siliceous, with flakes of a greenish-brown mica and 

 ferrite disseminated through it. 



At the top of the Kilik Pass, the water-parting between the 

 Pamirs and India, the dip is nearly vertical, with a slight dip to the 

 south. 



The study of the grits between Misgah and the Kilik Pass under 

 the microscope at once suggested that I had passed into a younger 

 series, and the same view occurred to my son in the field. He 

 also noted the striking change which the softer rocks introduced 

 into the aspect of the country. ' These loose grits/ he writes, 

 ' explain the formation of the flat Pamir valleys, and the easy slopes 

 and rounded tops of the ranges which fringe them, so different 



