BASS ROCK- BRAID HILLS. 77 



runs for a considerable way round the coast of East-Lothian, 

 of which Eyebroughy and the Bass Rock form the two ex- 

 tremities. The Bass Rock is composed of a very minute 

 greenstone, in which the felspar, which is compact and of a 

 reddish-brown colour, sometimes becomes so abundant, that 

 the rock almost passes into a compact felspar or a clinkstone. 

 Throughout its whole extent it exhibits more or less the 

 tabular structure, the concretions varying both in thickness 

 and mode of position. In several places, by the incessant 

 action of the waves upon the rock, caves have been produced, 

 one of which perforates it completely, and is accessible at 

 low water. 



Having noticed the relations of the several detached mass- 

 es of trap to the strata, we shall now describe in the same 

 way those clinkstones, claystones, and compact felspars, 

 which form a considerable portion of the Pentlands. The 

 hill of Blackford, which forms the northern termination 

 of this range, is entirely composed of clinkstone of a dark 

 grey colour : it contains in some places crystals of felspar, 

 and is traversed by veins of agate. The claystones 

 and compact felspars of the Braid Hills are of various 

 shades of grey, yellow, and brown, and are all easily de- 

 composed by atmospherical agents. Concerning the more 

 minute relations of these ignigenous masses to the stratified 

 formations, the completely covered state of the country ren- 

 ders it impossible to determine ; by examining, however, 

 the position of the strata in the few places where this can be 

 done, the result is, that all are found to abutt against the 

 unstratified rocks. In the Grange Quarry, which is situated 

 but a short distance from the clinkstone of Blackford, stra- 

 ta of red sandstone dip to the N. by E. at 40° ; and a coarse 

 conglomerate, which is visible for a few yards at Liberton- 

 brae, sinks to the E. S.E. at about 35°, exhibiting, in many 



