1823.] the principal Mountain Chains of Europe 7 



this zone in the interior cross its chains by transverse valleys in 

 order to reach the sea. Such is the condition of the Barrow, 

 the Suire, and the Blackwater. 



The veins branching off from the granite of the Wicklow 

 mountains are well displayed on the coast. 



The eastern portion of these chains has been excellently 

 described by Mr. Weaver. 



The Ocrinian chain of Devonshire and Cornwall, is the last 

 which remains to be noticed in the British isles. It extends 

 from Exmoor to the Land's End. It exhibits, 1. A. series of 

 granitic nuclei, of which the loftiest and most extensive is the 

 mountain plain of Dartmoor. The granite ramifies into the 

 incumbent slates, and the slate for a short distance from its 

 junction assumes an appearance approaching to gneiss, which 

 the Huttonians have considered as an alteration induced by the 

 contiguity of a heated mass. 2. Slates of a doubtful character 

 and sera (that is, whether primitive or transition) succeed, 

 abounding in metalliferous veins, and traversed by porphyritic 

 dykes. 3. Slates decidedly of transition associated with granu- 

 lar greywacke, transition limestone and greenstone occupy the 

 exterior of the groupe. Serpentine rocks also occur (in one 

 tract very extensively) probably as members of the decided tran- 

 sition series. The Ocrinian chain, like those of England gene- 

 rally, is destitute of gneiss and mica slate. 



Lundy Island, situated opposite the northern coast of this 

 chain in the middle of the Bristol channel, is a mass of granite 



(C.) Norman Isles, and North Western France. 



The Norman isles, which may almost be considered as a con- 

 necting link between the similarly constituted countries of Corn- 

 wall and the Cotentin, are principally granitic. 1. Guernsey 

 presents granite and granitelle in the northern, and gneiss in the 

 southern division. 2. Jersey in its higher and northern tract 

 consists of granite, in its southern and lower of slate reposing on 

 it. 3. Alderney has on the south-west cliffs of porphyry, on the 

 north-east low shores of a grit formed from granitic detritus. 

 4. Sercq exhibits trap rocks on the west, and sienite on the 

 south. — (See account of these isles by Dr. Mac Culloch, Geol. 

 Trans, vol. i.) 



Chains of Bretagne and La Vendee. — These appear in the 

 nature of their constituent rocks and metalliferous deposits to 

 bear a near resemblance to the Cornish chains. In the Cotentin 

 the granite appears in some places decidedly to rest upon the clay 

 slate ; both these rocks alternating with quartz rock, porphyry, 

 and sienite. Much, if not all, of this clay slate is evidently that 

 of transition ; in the shafts of the argentiferous lead mine of Huel 

 Goatterebratulre (spiriferae?)have been found in it, and at Angers, 

 trilobites occur. In La Vendee, the granitic rocks appear to 

 predominate. A line drawn from Cherbourg by Alcncoii, 



