MUCK. GEOLOGY. 525 



it undergoes no change ; as if disproving in the one place 

 that influence of the trap, which in another it appears to 

 confirm. 



But if the chemical or mineralogical variations of the 

 limestone prove nothing with regard to this influence, it is 

 not so with the mechanical derangements. Where the 

 veins are most numerous, the limestone is broken into 

 pieces and entangled in them, while the directions of the 

 strata are at the same time reversed ; from horizontal 

 becoming perpendicular. Solitary fragments of a few 

 inches in diameter are also found insulated in the basalt. 

 These disturbances are not much unlike those which in 

 Glen Tilt take place at the junction of the granite with the 

 stratified rocks, and still more resemble others which will 

 hereafter be pointed out in Seil and in Bute. 



Among the trap veins I observed a substance forming 

 what seemed to be a disturbed portion of a bed. It is 

 a sort of chert exceedingly brittle and sharp in the frag- 

 ments, very much resembling that which is involved in the 

 pitchstone vein of Egg. It will be recollected that the 

 same rock occurs among the limestone on the east side of 

 Sky, and that it was there proved to depend on the 

 influence of the surrounding trap, while the accompanying 

 shale was in the same circumstances converted into sili- 

 ceous schist. There can be little doubt that the portion 

 of chert here described has also been a fragment of one 

 of the calcareous beds, owing its present induration to the 

 same cause as its position, namely, the intrusion of the 

 trap vein. 



On reviewing this insulated portion of secondary strata 

 there can be no hesitation in referring it to the same 

 formation as those of Egg, namely, the lias series. 

 Although it presents no organic remains capable of esta- 

 blishing this identity, the general appearance of the beds 

 is almost sufficient to prove this correspondence. If to 

 that be added the absolute resemblance of the several 

 substances to those which occur in that series in different 



