Ch. VI.] PRIMARY ROCKS. 115 



the laminae of the former rock, which are every where bent 

 over them, as if they had, in a soft state, been moulded on 

 the previously indurated concretions. * So likewise near 

 Drontheim, Norway, in a rock intermediate between mica- 

 slate and clay -slate, folia of mica surround kernels, which 

 are very hard and compact, and appear to be a granular 

 mixture of compact felspar, a little quartz, and fine scales of 

 mica. The kernels, with their envelope of mica, are of 

 various sizes, sometimes equal to two or three feet in diameter : 

 these concretions lie close together, forming whole rocks. 

 In Cornwall, the compact variety of chlorite-schist near 

 Relistian mine exhibits this conglomerated structure : its 

 nodules are not globular, but flattened, and are composed of 

 concentric layers, the outer ones being softer and more chlo- 

 ride, the central more compact and crystalline. 



Many examples of this conglomerate have been recorded : 

 that of Valorsine is particularly noted, and is regarded as a 

 detrital rock ; but if it alternates with gneiss, as has been 

 stated, it is probably of the same nature as those just enumer- 

 ated. " The lower part of the Col de Balme, according to 

 Saussure, as quoted by Dr. Kidd, is a moderately grained 

 grey granite ; above which are rocks intermediate to gneiss 

 and mica-slate : higher up are beds of a grey and sometimes 

 greenish slate, containing a great quantity of rolled pebbles, 

 some angular and others rounded, varying from the size of 

 sand to masses of six or seven inches in diameter. Some of 

 the beds are very thin, remarkably fine grained and micaceous, 

 and entirely free from pebbles ; others are of considerable 

 thickness, and filled with pebbles." Brongniart, also, in the 

 Cotentin, in Brittany, observed a similar fact. A series of 

 granitic and syenitic rocks is followed by a shining argilla- 

 ceous slate of a greenish colour, the laminae of which gradually 

 becoming more and more undulated, and traversed by veins 

 of quartz, and penetrated with oval nodules of the same 



* Western Isles of Scotland, vol. i. p. G4. 

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