the Neighbourhood of Kelso. 147 



has been deposited by water. An interesting example of such a 

 formation occurs a few miles to the north-east of the beautifully 

 placed village of Festiniog, near some small lakes, where a rock, 

 is found, composed of fragments of black slate and steaschist, 

 united by a felspathic cement. This breccia has evidently been 

 exposed to a violent heat, and as it lies over, and graduates into, 

 an extensive bed of felspar, similar to its cement, while the frag- 

 ments, in this place at least, exhibit the marks of having suffered 

 from friction ; it has probably been chiefly formed by the action 

 of water on the heated mass of felspar, to which it has conveyed 

 the black slate and steaschist. In one part of this breccia, I 

 found the fragments blended with each other as if they had 

 been fused, forming a compact mass, without the intervention of 

 any cement ; a proof of the violent heat to which they have been 

 exposed. This brief notice of the more remarkable instances 

 that I observed in Wales, of the passage of a pyrogenous into a 

 fragmentary, or apparently fragmentary, rock, may serve to 

 shew that the question, whether a rock be metamorphic or not, 

 is sometimes difficult to decide. The causes to which I have 

 attributed the mixed and doubtful character of these Welsh 

 rocks, have seldom acted singly ; they have more frequently 

 united in forming the same mass, rendering its appearance very 

 variable. This has been the case in the rocks to which I have 

 referred, near Pwllheli and Festiniog, which are extensive ; and 

 we constantly meet others in this interesting district, whose re- 

 markable and variable characters can be accounted for only by 

 supposing that all the circumstances mentioned, have attended 

 their formation. This is also what might be expected, where 

 many of the pyrogenous rocks, after breaking through soft 

 slates, were immediately exposed to the action of water. Under 

 circumstances equally varied, appears to have been formed the 

 very remarkable greenish rock, by some geologists called grey- 

 wacke, to which the English lake district is so much indebted 

 for its beauty. It spreads over a considerable extent of country, 

 presenting the characters of fragmentary, concretionary, and 

 pyrogenous rocks ; always, however, retaining that similarity of 

 appearance, which proves that the whole belongs to the same 

 formation. What appear, at first sight, to be fragments in this 

 rock, are often flattened concretions, usually of chlorite ; and, 



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