398 SKY. GEOLOGY. TRAP VEINS. 



to be considered as prolongations of the former, it is 

 impossible to determine ; although they are probably the 

 same. 



The courses of trap veins are frequently attended by 

 disturbances in the including strata, but the present 

 instance affords a remarkable exception. Although so 

 numerous in Strathaird, no disturbance occurs in the sand- 

 stone beds ; their regularity being the same in the upper 

 parts of the coast where the veins abound, as near 

 its southern extremity where they are nearly altogether 

 absent. Perhaps their absence at this place may be 

 considered as strengthening the notion that they originate 

 in the superincumbent trap, which does not extend towards 

 the end of the promontory. Although no particular in- 

 duration or change of texture occurs immediately at the 

 contact of the veins with the strata, yet it must be 

 remembered that the whole mass is of a hard quality 

 where the veins abound, and of the usual soft texture 

 where they are wanting. 



Before quitting this subject it is necessary to point 

 out one extraordinary effect that must have resulted from 

 the intrusion of these veins. Whatever proportion, col- 

 lectively taken, they may bear in breadth to the lateral 

 dimension of the strata which they intersect, it is plain 

 that the whole mass of strata must have undergone a 

 lateral extension equal to that quantity; a motion so 

 great as not to be easily reconciled with the present 

 regularity of the whole. It is also a singular circum- 

 stance, that on the opposed shore of Sleat a different 

 effect takes place, and proportioned, it would here seem, 

 to the number of the veins ; the red sandstone strata 

 of this coast being often turned from a slightly inclined 

 into a vertical direction, with other considerable marks 

 of disturbance. It is impossible to account for these 

 apparently capricious differences, and we must for the 

 present be content to rank them among the numerous 

 unexplained appearances in which the science abounds. 



