150 Mr Le Hunte on the Geology of 



ter is imperfectly developed, sub-globular concretions supplying 

 the place of crystals. In the very shght examination of these 

 hills, however, that my time enabled me to make, I saw nothing 

 so very peculiar in the characters of the porphyry, as to lead me 

 beyond a suspicion that it was formed from the sandstone ; for 

 I recollected that the latter, when fine-grained, might closely 

 resemble the paste of a clay-stone porphyry, while the similarity 

 of colour, although striking, might be accidental. Having heard 

 that the remains of a vitrified wall existed on the Black Hill, near 

 Earlston, 1 resolved to visit it, and here my suspicion was car- 

 ried to conviction, in spite, I may truly say, of frequently re- 

 curring incredulity. This hill is said to be 1200 feet above the 

 sea-level ; but it is not much higher than the sandstone which 

 forms the greater part of its steep western side ; while its sum- 

 mit is formed of porphyry, as well as its eastern declivity, which 

 is so gradual that it is occupied by a luxuriant field of turnips. 

 Excepting in one spot, on the western declivity of the hill, 

 where it rests on the sandstone which it has slightly altered, 

 there is no large continuous mass of the porphyry visible ; but 

 it frequently appears above the surface, which is generally 

 covered by its fragments. I twice visited this remarkable hill, 

 and every step I took upon it, every stroke of my hammer, 

 served to remove the incredulity I had previously felt, and to 

 convince me that my opinion, as to the origin of the porphyry, 

 was well founded. It is difficult to state, in words, all the evi- 

 dence which influences the mind in inquiries of this nature ; for 

 it often consists in minute resemblances that cannot be described. 

 I must be satisfied by saying, that I collected specimens from 

 different parts of the hill, that plainly exhibited a passage from 

 the sandstone, through various degrees of change, into the por- 

 phyry. The similarity of colour in the two rocks, usually a 

 blood red, while it had some influence on my opinion, made me 

 hesitate to adopt it, as it is common both in sandstone and por- 

 phyries ; but having now observed it in three places, distant from 

 each other, I could not avoid giving it more weight. The por- 

 phyry here, however, varies in colour, through difi'erent shades 

 of red and impure yellow, while it is occasionally spotted ; just 

 what might be expected, supposing my opinion to be correct. 



