MULL. GEOLOGY. 577 



occasionally in such abundance as nearly to equal in 

 quantity the stone which contains them, and I must 

 remark that they are rarely known to occur in the clay- 

 stones of this character. 



As in Sky and in Arran, many other varieties of trap 

 are found among the mountains of this district, but it is 

 unnecessary here to enter into any details respecting these. 

 Enough has been said of them in a geological view, and 

 I shall on some future occasion have a better opportunity 

 of discussing this subject as far as regards the nature and 

 distinctions of the mineralogical varieties. 



Connected with these rocks is found a considerable 

 tract of the same syenite which forms so conspicuous 

 a feature in Sky. It may be traced through the hills 

 Ben y chat, Ben greig, and Cruach ruilin ; and, from the 

 indications given at a distance by the contrast of its red-^ 

 dish colour with the blue tint of the rocks last described, 

 it appears to occupy a considerable portion of the imprac- 

 ticable country to the eastward. It is more easy in this 

 place than in Sky to trace its connexion with those rocks. 

 The change may be observed in Ben y chat, and, at the 

 place where it is effected, the blue rock first passes into a 

 brown variety, the character of which is very distinctly 

 marked and resembles precisely that of an analogous rock 

 which occurs abundantly in Arran and in Lamlash. The 

 transition from this to the syenite, immediately follows, 

 without any apparent irregularity of the very obscure beds 

 which form each, and without any evident discontinuity 

 except in colour. The change of the one substance to the 

 other in the very same bed is not so gradual here as in 

 Rum. It bears however no resemblance to a superposition 

 of distinct rocks ; since there is no greater regularity in the 

 beds than that which occurs in granite, and as at a lower 

 point in the hill, the syenite once more gives way to 

 the claystone. This example, when compared with the 

 transitions of the analogous rocks in Rum and St. Kilda, 

 and the probable circumstances of the same nature occur- 



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