part 3] PAMTIt EARTHQUAKE OF FE13EUATCV 1911. 243 



forming a huge barrage which seemed to rise 1200 feet above 

 the level of the lake. 



Some idea of the difficulty of this journey may be formed from 

 the fact that the distance, which it took three days to cover, is less 

 than 15 miles ; while the same distance, above the barrier, was 

 covered in one day, although the going was still bad and only 

 practicable on foot, and by men accustomed to mountain-climbing. 



The foregoing account shows that the great landslip of Usoi was 

 not the only one that accompanied this earthquake ; it was by far 

 the largest, but there were innumerable others, many of which can 

 only be regarded as small in comparison with the exceptionally large 

 one, and the accounts reproduced by Col. Spilko show that, besides 

 those seen by Sir Aurel Stein, landslips occurred, on a similar scale, 

 at least as far downstream from the junction of the Taniinas and 

 Murghab. In part, this extensive development of landslips must 

 be ascribed to the unstable, or semistable, condition of the steep 

 slopes on each side of the deep-cut valley through a lofty 

 mountain-region. Landslips, in fact, are by no means unknown in 

 this region, and Colonel Spilko quotes, and accepts, the statement 

 that the Yashil Kul, in the Ghunt valley (south of the Murghab), 

 was caused by an ancient landslip of great size ; yet the simul- 

 taneous occurrence of so many landslips over so large an area, as 

 took place on the night of the 18th of February 1911, requires 

 some common determining cause, which is to be found in the 

 severe earthquake, known to have coincided with the fall of these 

 landslips. 



There remains, however, the possibility that the great slip at 

 Usoi might have been the primary cause of the earthquake, and so 

 of the other landslips. This supposition is negatived by the fact 

 that the great slip is not situated at, or near, the centre, but on 

 the extreme limit of the region of greatest destruction. The 

 time of occurrence of a landslip may be determined by an 

 earthquake, but the magnitude is very little influenced by it; 

 in the case of those landslips, which can only be x-egarded as small 

 when compared with the unusual magnitude of the Usoi slip, it 

 may be taken as certain that slips were in preparation, and that 

 sooner or later they would have fallen in very much the same 

 magnitude, a magnitude determined by those initial cracks with 

 which such mountain-slips commence. Even the great Usoi slip 

 had probably been in preparation, in the same way, and would 

 have come down in due course of time; its size, therefore, does not 

 indicate a greater violence of earthquake. The position of the 

 Usoi slip is, consequent^, quite consistent with the conclusion 

 that it, and all the other effects, were due to the earthquake as a 

 common cause : it is not consistent with the supposition that the 

 slip was the cause of the earthquake. 



Besides the particular argument from the position of the Usoi 

 landslip, with regard to the area over which the earthquake 



