82 GEOLOGY OF THE LOTHIANS. 



Concerning the appearances which the conglomerate exhi- 

 bits, when near these veins, 'it may be remarked, that they 

 are the same as many which we have before described as 

 attending similar rocks in similar situations; it become- 

 intensely indurated, and has a more or less perfect conchoi- 

 dal surface. The felspar of Black Hill is found to contain 

 imbedded masses of this conglomerate many yards in extent, 

 and on its eastern side, near the farm of Craigentarrie, strata 

 of red sandstone are found in an almost vertical position ; 

 slate the same as that of Habbie's How is also to be observed 

 in several places intimately connected with the compact fel- 

 spar. 



Besides all these interesting relations of stratified to un- 

 stratified rocks, we have, in the formation of the valley 

 which separates the hill of felspar from the conglomerate 

 of Habbie's How, a subject of considerable interest, and an 

 example of one of the many valleys which cannot be satis- 

 factorily explained by referring them to the long-continued 

 action of the streams which traverse them. In specula- 

 ting upon the origin of valleys, it is necessary to examine 

 whether these have been produced by actions aqueous or 

 igneous, and subsequent to the formation of the rocks which 

 they traverse, or whether they are to be considered as origi- 

 nal depressions. In regard to the valley of Glencorse, the 

 relations of the several rocks which we have just noticed, 

 render it evident that it is not an original depression, but 

 that subsequent actions, whether aqueous or igneous, have 

 produced the existing arrangements. That this valley 

 has been formed by the long-continued action of the insig- 

 nificant stream which at present runs through it, is, as we 

 have just remarked, highly improbable ; on the contrary, 

 however, it and all other valleys, presenting the same cha- 

 racters, may be satisfactorily explained by considering them 

 as having originated in more or less limited lines of fracture. 



