1 842.] of the Himmalaya Mountains. cxlv 



entireness of this formation. These varieties, at least all those that 

 required it, have been described already with sufficient minuteness. It 

 may be here a sufficient recapitulation to say, that the argillaceous 

 schist, as it covers the greatest extent, so it presents the greatest vacilla- 

 tion in character. No opinion can be more void of foundation than 

 that which supposes the several varieties of clay slate to be arranged 

 under four different, distinct, and well marked types, the produce of 

 four different eras, and distinguishable by characters mainly dependent 

 on colour; so far from dividing into regular zones, or even isolated 

 patches, the different varieties are found in every part of this extensive 

 tract. Excellent purple roof slate ; stone slate passing into flinty slate; a 

 black almost arenaceous rock, with patches of white resembling the ash 

 of half-burned charcoal ; a white arenaceous rock with scales of mica ; a 

 soft schistose clayey rock of various bright colours, and a granular yellow 

 rotten stone ; all these are found in a space of not three miles square. 

 From my own very limited experience, I would say, that of all distinc- 

 tions, colour in clay slate is the most vague, and least to be depended on. 



307. This tract of schists contains numerous and extensive beds of 

 limestone, frequently enclosing veins of galena, (hexahedral lead galena 

 of Mohs,) beds of dolomite (macrotypus lime haloide,) and potstone 

 (prismatic talc mica, the massive variety,) either singly or in conjunc- 

 tion, and containing in each case veins of copper and iron pyrites, 

 (pyramidal copper pyrites and hexahedral iron pyrites,) purple and 

 grey copper (octahedral copper pyrites and tetrahedral copper galena,) 

 beds of red and brown iron ore (rhombohedral and prismatic iron ores,) 

 veins or beds of graphite, (rhombohedral graphite mica,) and superficial 

 amorphous masses of gypsum (prismatoidal gypsum haloide.) But the 

 most remarkable of all its subordinate mineral masses is the greenstone, 

 which is so often met with, though limited as to extent. Connected 

 probably with this rock is the series of fragments, obtained near 

 Bhumowree, presenting types of amygdaloid and porphyry. But the 

 whole subject is as obscure, from want of observation, as it is in- 

 teresting, and the fact of the only series of lakes within these mountains 

 being found in the neighbourhood, enhances the interest extremely. 

 Indeed, it is not a little difficult to restrain our premature efforts to con- 

 nect these facts with a well-known theory, remarkable for the origin it 

 assigns to these rocks. 



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