. Calcutta Journal of Natural History. 566 Notes on Geology and Mineralogy of Afghanistan. wasting appearance, and are in many places fading away rapidly under the influence of atmospheric agents, and some indeed have been entirely swept off, leaving nothing but a broad base of pebbles confusedly mingled together, and affording specimens of nearly every rock to be met with in the neighbouring mountains. In some parts again they appear to be imperfectly consolidated or semi-indurated, exhibiting indications of stratification, but usually they are composed of stiff reddish clays alternating with
. Calcutta Journal of Natural History. 566 Notes on Geology and Mineralogy of Afghanistan. wasting appearance, and are in many places fading away rapidly under the influence of atmospheric agents, and some indeed have been entirely swept off, leaving nothing but a broad base of pebbles confusedly mingled together, and affording specimens of nearly every rock to be met with in the neighbouring mountains. In some parts again they appear to be imperfectly consolidated or semi-indurated, exhibiting indications of stratification, but usually they are composed of stiff reddish clays alternating with ioose textured sand- stones, the clays being often horizontally divided by their layers and detached masses of foliated gypsum^ of a pure and glossy transparency. From the situation of these crumbling hills, opposite to the openings of the mountain glens, many would perhaps be, led to attribute them to the agency of glaciers in former years, were it not that their stratification is opposed to such a doctrine, and we have moreover no data from which to infer the existence of a colder climate over these tracts in former ages, than now. My own impression is, that they belong truly to the tertiary period, of which both the Bolan Pass and the Shawl district possess some deposits. It is probable that the destruction of these hills, composed as they are of friable sandstones and beds of clay, has fur- nished in modern times a great portion of the soil of the desert tract of Cutchi, for the materials of that arid plain are arenaceous clays, containing particles of foliated gypsum. The decay in these outlying hills is not however to be attri- buted to any more violent agents than are now furnished by the atmosphere; for their destruction is still going on gra- dually and surely, and it is probable that a great portion of the less indurated strata will eventually disappear. The upper stratum is generally an indurated sandstone of a brownish colour, while the underlying beds are of far g
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