502 proceedings oe the geological society, [june 11, 



Discussion. 



Mr. Peestwich could hardly understand how, without a very close 

 examination, it could be ascertained that there were no outlets from 

 the plains which had been mentioned. If by any possibility there 

 were such outlets, great difficulty would arise in accepting the theory. 

 He was not quite satisfied as to the evidence of the thickness of the 

 deposits on the slopes, and inquired as to the presence of organic 

 remains. 



Prof. Ramsay had been much struck with the paper, though it 

 was confessedly a rapid sketch of the country. Persia might 

 indeed be regarded as a typical example in an exaggerated form of 

 what was taking place in all dry areas. There are scattered inland 

 salt lakes and large tracts of desert sands, surrounded by immense 

 mountain -ranges, suggestive of areas like those of the Dead Sea, 

 the Caspian, and the Aral, in which the evaporation equalled the 

 supply of water derived from the rainfall, and where in consequence 

 the lakes were salt. In many cases such lakes had become filled with 

 sediment, while others have absolutely ceased to exist from want of 

 rainfall. As to the causes of the formation of the gravels, he agreed 

 with the author that on so large a scale any ordinary river-theory 

 appeared almost inapplicable, and he was content to confess that at 

 present it appeared to him difficult to account for their existence. 

 The history of the Oxus was well known ; and its banks had been 

 the scene of constant invasion and disturbance, though they had in 

 early times been occupied by large populations. He thought that in 

 old times the Oxus might have been banked up, like most rivers 

 along which there is an extensive population, and that possibly it 

 was in consequence of the giving way of such banks that its course 

 had been altered. Its condition might, he thought, have been like 

 that of the Po at the present day, the bed of which was now above 

 the neighbouring plains, and which a few years' neglect would divert 

 from its course, so as to cover the surrounding country with ruin. 



Mr. Blanfokd, in reply, stated that from the small plains there 

 were certainly no outlets, and that in all probability there was none 

 also from the great central plain of Persia. This had, indeed, been 

 barometrically surveyed in various directions, and it was found 

 that a large part of its centre was at a lower level than any part of 

 the surrounding country. The slope of gravel at the edges of the 

 deserts usually rested on the lacustrine deposits ; and though there 

 was in some cases a difference of 2000 feet between their highest 

 and lowest parts, it was impossible to speak with certainty as to 

 their absolute thickness. He was not aware of any organic remains 

 having been found in the deposits ; but they had as yet been but 

 little examined. Though the majority of the lakes were decidedly 

 salt, there were two exceptions — the lake of Goksha and that of 

 Sistan. The greater portion of this latter was now dried up ; and 

 though there was no outlet to the remaining portion, it was perfectly 

 fresh. For this circumstance he was not prepared to account ; but 

 there appeared to be no doubt on the subject. With regard to the 



