Notes on Geology and Mineralogy of Affghanistan. 579 



up by some internal volcanic movement. Powerful they 

 must have been, or they could never have moved the vast 

 boulders which are visible in the bed of the Passes. 



Had lakes occupied the basin-like portions of these defiles, 

 the deposits instead of being rolled stones and boulders, 

 would have consisted of earthy particles, such as silts, clays, 

 and mud ; whereas the presence of blocks many tons in weight, 

 together with the general stony character of the deposits, 

 proves that violent action has been employed, for none other 

 could have moved such masses. Wells sunk at the lower 

 end of the Bolan Pass, would pass through beds of rolled 

 pebbles like those at Jumrood, while a few miles farther 

 removed the silts and clays of alluvial plains would be met 

 with ; but these facts are by no means sufficient to authorise 

 the inference that lakes once existed in the bosom of the 

 defiles which now constitute the Khyber and Bolan Passes, 

 nor can the water-worn appearance of the pebbles be con- 

 sidered to favour the hypothesis, for such rounding must 

 have occurred previous to the deposition of the conglome- 

 rates from which the pebbles are derived, and that deposi- 

 tion was evidently anterior to the elevation of the secondary 

 rocks since they are seen to rest conformably upon them. 

 These secondary rocks being of marine origin, must neces- 

 sarily have been beneath the waves at the time when the 

 convulsion, which elevated them into lofty dry land, took 

 place, and the retreat of the displaced waters through the 

 glens and valleys then formed, would have been fully equal 

 to produce all the effects visible in these Passes, without 

 any necessity for calling in the after aid of fresh-water lakes, 

 which in the Bolan Pass at least, I feel quite certain never 

 had existence. 



To return then from this digression. It may be briefly 

 stated, that the mountainous country situated between the 

 plains of Cutchi and Affghanistan, is composed of secondary 

 rocks, overlaid by tertiary and diluvial strata in a con- 



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