450 MR MILNE ON THE GEOLOGY OF ROXBURGHSHIRE. 



Cheviots. It is impossible to describe all the varieties, they are so numerous, 

 and so complex in themselves, of porphyry which abound in these hills. I am 

 not aware of there being any greenstone or basalt among them. The rock con- 

 sists almost entirely of clay and felspar, exhibiting in general an earthy, seldom 

 a compact or crystalline structure. The latter variety seems to occur only in the 

 very central parts of the range, composing several entire hills near Hownam, Atton- 

 burn, and Yetholm. The rock of these hills has a dark resinous appearance, and 

 exhibits sometimes a conchoidal fracture. When struck with the hammer, it rings 

 like metal. It is occasionally striped with iron-shot veins of quartz, which afford 

 a pleasing contrast with the black resinous lustre of the rock. It does not easily 

 decompose, and has been used with advantage as a building stone. 



The Cheviot porphyries, which present an earthy structure, are generally 

 filled with veins and nodules of quartz. These nodules are often reddened with 

 iron, and, when large, receive the popular name of jasper. Such masses are ex- 

 tracted on the west bank of the Jed, about a mile to the west of Edgerstone, not 

 far from Shaws farm-house. The colours of the earthy porphyries of Cheviot are 

 brown, lilac, purple, grey, and inclining to red. I have never seen any porphyries 

 of the brick-red colour, common in the Eildon hills. 



That the Cheviots were thrown up before the deposition of the red sandstone 

 formation, is evident from several circumstances. (1.) At Lin ton Church, near 

 Morebattle, the conglomerate of the old red sandstone may be seen almost in con- 

 tact with the Cheviot porphyry, and perfectly horizontal. The pebbles of the 

 conglomerate are chiefly porphyritic. (2.) On Jed water, about two miles west of 

 Kdgerstone, and opposite to the farm of Shaws, there are sandstone strata which 

 appear to lie above the old red sandstone conglomerate existing on that farm. 

 These sandstone strata are within twenty yards of the Cheviot porplryry, and unaf- 

 fected by it. Moreover, they contain rounded pebbles of Cheviot porphyry. Be- 

 sides being seen so close to the igneous rock, they can, higher up the river, be traced 

 to within a few yards of the greywacke strata, which there run E. by S., 

 dipping at an angle of 86 to the south. At this place there is little or no iron 

 in the greywacke, which probably explains the brownish-yellow colour of the 

 sandstones just referred to. The greywacke strata are here, and farther down 

 the river, of exactly the same yellowish colour. (3.) At Cherry trees, near Yetholm, 

 the old red sandstone strata are quite horizontal, and quite close to the compact 

 felspar porphyry, of which the hill there is composed, and seem to have been in 

 no way affected by it. (4.) At Blakelaw there is a thick bed of conglomerate, 

 composed of porphyry and greywacke pebbles, and close to a hill of claystone 

 porphyry, which has apparently not altered it. 



Eildon Hills. The westermost hill, on which the Cairn stands, consists of a 

 very hard clinkstone, having a grey basis, and small crystals of felspar inter- 

 spersed through it. It strikes fire with steel. On the eastmost hill, the rock, 

 though much the same, is not quite so hard. I have specimens of this rock, con- 



