the Neighbourhood of Kelso. 149 



the latter opinion appears the more probable; but there are 

 cases in which it seems necessary to adopt the former; nor is it 

 unlikely, that while the coarser matter was softened by heat, the 

 finely divided formed concretions. In such rocks, we often find 

 that the pebbles, although tolerai)ly large, fit into each other, 

 leaving no intervening space; while the fragmentary character 

 occasionally disappears, and the mass becomes crystalline. 

 They occasionally contain cubic pyrites, generally in small crys- 

 tals; but I once found a large one, which was easily dislodged, 

 leaving a cast, whose sides were smooth and brilliant as glass; 

 a plain proof that the coarse, siliceous particles, of which the 

 rock is composed, were soft when the crystal was formed. This 

 fact is the more interesting, because the mass in which it was 

 observed has the ordinary characters of a conglomerate, rarely 

 exhibiting any other proof of its having been sol't : it is the same 

 which, regularly stratified, we pass over, for a considerable dis- 

 tance, in ascending Snowdon from Llanberis.* Decidedly con- 

 cretionary rocks are more common than is generally believed. 

 The upper part of the gneiss in Bute, near the Kyles, is the 

 most interesting example that I have seen. The quartz and 

 felspar are indistinct, and rather large concretions wedged in- 

 to each other. This graduates into a coarse sandstone, similar 

 in composition, which is probnbly also concretionary. A chlorite- 

 slate, similar to this gneiss, is found in Dumbartonshire. There 

 is reason to believe, that what Dr M*Culloch considered frag- 

 nientary beds among the primary rocks of the wer.t of Scotland, 

 are concretionary. But my space compels me to return to 

 Tvveeddale. 



From Kelso I visited the beautiful remains of Melrose Abbey, 

 and, having a little time to spare, ascended the Eildon Hills. On 

 examining, in such quarries as I met, and they extend from 

 their base to a considerable height, I could not avoid very 

 strongly suspecting, that the porphyry of which they are chiefly 

 composed, was derived from the red sandstone, altered by heat. 

 In some places the rock is not porphyritic, but has the appear- 

 ance of a hardened sandstone ; in others the porphyritic charac- 



* May not steam, under pressure, have contributed to soften and alter 



rocks \ 



