1841.] Capt. HullorCs Geological Report. 209 



The dip of the strata is now uniformly to the S. W., and generally at an 

 angle of 45°, though here and there they rise abruptly to a nearly vertical 

 position, denoting an excess of the upheaving forces from below. As we 

 approach Larree after crossing the Gew river, the bed of which is of grey- 

 ivacke slate, we come upon a thick stratum of pure white quartz rock, which 

 appears to be a continuation of the same rock which was seen at Leeo on 

 the opposite side of the range ; in contact with this, and immediately rest- 

 ing upon it, is another bed of siliceous rock, which passes gradually into 

 thin strata of flinty slate. Upon this rests clay slate, which then alternates 

 frequently with greywacke and sandstones. Further on we perceive masses 

 of gypseous breccia formed of angular fragments of argillaceous schists, encrusted 

 or cemented together by gypsum. This rock, if it be entitled to the name, 

 owes its origin to the same waters which deposited the gypsum beds of 

 Chungo and Skialkur ; it is found overlying the edges of the true strata 

 from which it has been formed, and occurs in rude and mis-shapen masses. 

 To this breccia I would also call attention, as serving to shew a change in 

 the waters of the lake, or at all events a decrease in the proportion of 

 their saline properties. Farther on still, and nearly opposite the village of 

 Somra, a stratum of trap is seen to occur between shales above and sand- 

 stone below ; it is conformable to the true strata with which it is clearly in- 

 terstratified, not causing any dislocation of the series. Beyond Larree, how- 

 ever, the same rock occurs again, in one place interstratified with grey- 

 wacke and dark blue limestone, at another running up vertically in an 

 amorphous mass through the strata, which it first dislocates and then over- 

 lies. In this case, the strata on either side of the Spiti dip to the S. W., 

 while the rocks through which the trap has more immediately passed or 

 been injected, are thrown boldly and abruptly from the usual course to the 

 westward. The strata on the opposite side of the river are at the same- 

 time raised from the angle of 45° nearly to a horizontal position, and af- 

 ter some twisting of the strata, again with apparent difficulty regain their 

 wonted S. W. dip. Here it is evident that the trap in question has been 

 the molten vein whose struggles to burst upwards through the superin- 

 cumbent weight of strata has been the agent which has thrown them 

 into their present inclined positions, and in its upward course has first be- 

 come partially interstratified with those which possessed the least indura- 

 tion or means of resistance, and then finally, as it burst through all obsta- 

 cles, flowed over them in a broad sheet of molten matter, which as it cooled 

 assumed the present solid and compact texture. 



Of such having been the fact, we observe proof in the vein of vertical 

 trap acting as a support, or upright as it were, from which the strata 

 now incline and dip downwards. 



