78 GEOLOGY OF THE LOTHIANS. 



places, signs of disorder. Near the village of Burdie-house, 

 and at Straiton Mill, the coal formation sandstone, and 

 a bed of the mountain limestone, plunge to the S. S.E. at 

 40° and 35°. To the west of the Braid Hills, and sepa- 

 rated from them by about half a mile of gently undulating 

 country, the hill of Craig-Lockhart rises, and on its east 

 side the red sandstone which occurs at the Grange, is to 

 be observed dipping W. at 35°. The rock which forms 

 the igneous portion of Craig-Lockhart, is, in some places, a 

 well-marked greenstone, exhibiting an imperfect columnar 

 structure ; while in others it approaches to basalt, contain- 

 ing numerous small crystals of velvet-black basaltic horn- 

 blende, and a few large crystals of glassy-white felspar. 

 Within the space of a few feet, this rock passes into a 

 greenstone of an earthy aspect, which makes a transition in 

 some parts into a claystone, and in others into a wacke. 

 The claystone into which the greenstone passes is, in gene- 

 ral, of a greyish colour, and contains crystals of black horn- 

 blende, the crystalline form of which may often be exposed 

 on a favourable fracture ; contemporaneous veins of felspar 

 traverse the rock in many places. In some parts of the 

 hill a fine greenstone is found, which contains large and 

 well-defined crystals of felspar, and resembles, in some de- 

 gree, the green porphyry of the ancients; while in other parts 

 a trap-tufa occurs, which is always distinctly stratified. On 

 the side of the Colinton road, the sandstone strata dip N. 

 W. at 30°, thus abutting against the trap of Craig-Lockhart. 

 The Pentland Hills,* as we have already said, rise im- 

 mediately to the south of the Braid Hills, forming nume- 

 rous rounded and conical summits, and attaining, in some 



* Vide Memoirs of the Wernerian Natural History Society, vol. 2d, 

 for Professor Jameson's outline of the Mineralogy of the Pentland Hills ; 

 and Dr Charles Mackenzie on tbe compact felspar of the Pentlands in 

 vol. i. Wernerian Memoirs. 



