THE PENTLANDS. 79 



instances, to the heights of 1876 feet and 1856 feet. Mi- 

 neralogically, they may be separated into two series of 

 hills, viz. that composed of felspathic rocks, and that formed 

 of sandstone ; the former class constitutes the eastern half 

 of the range, while the latter occurs chiefly in the western. 

 As in the Braid Hills, the ignigenous portion of the Pent- 

 lands is composed principally of various porphyries, clay- 

 stones, and compact felspars, all of which pass into one an- 

 other, and preserve in their several relations no definite 

 mode of grouping, inasmuch as the formation of all appears 

 to have been strictly contemporaneous. A greenish-grey 

 clinkstone occurs in several places, and in other parts a com- 

 pact felspar is to be met with, which varies in colour from 

 flesh to brownish-red, and by assuming crystals of felspar, 

 makes, in some places, a transition into porphyry. Clay- 

 stone of various colours forms many of the Pentland hills, 

 and exists in all stages between an easily friable rock, 

 and one of considerable solidity ; very generally, it is as- 

 sociated with the porphyritic structure, the felspar crystals 

 in some instances being of considerable size. Besides this 

 claystone exhibiting the porphyritic arrangement, it be- 

 comes frequently amygdaloidal, and contains concretionary 

 masses of calcareous spar, amethyst, quartz, chalcedony, 

 agate, lithomarge, and green- earth. Of the claystone of 

 the Pentlands, one only may be noticed more particularly, 

 in as much as its characters might easily cause its true na- 

 ture to be mistaken ; it forms the whole of the hill of Kirk- 

 yetton, and occurs also in the Turnhouse hill. On exa- 

 mining this rock at first sight, it will appear as if composed 

 of fragments of compact felspar and claystone ; but, after 

 studying it minutely and in all its details, these fragments 

 will be discovered to be such in appearance only. The same 

 varieties of the compact felspar, which in some places might 

 be easily mistaken for fragments, are found in others to 



