CAMBRIAN. 



Fig. 7. — Penrhyn Slate Quarry. (From a photograph.) 



The term Cambrian, proposed by Sedgwick, is derived from 

 Cambria, the old name for Wales, and in its broadest sense it 

 is equivalent in part to the ' Cumbrian ' series of the Lake 

 District. 



Sedgwick's earlier observations on the Lake District were 

 made during the summers of 1 822-1 824, but he remarks that we 

 owe our first knowledge of the larger subdivisions of the rocks to 

 Jonathan Otley of Keswick. Thus three groups — i, Skiddaw 

 Slate; 2, Green Slate and Porphyry; and 3, Rocks below the Scar 

 limestone, originally distinguished by Otley in 1820, were adopted 

 by Sedgwick as the basis of his classification. John Phillips 

 mentions a meeting with the celebrated Professor in 1822 ; he was 

 riding, as usual, with saddle-bags for his specimens, and a miner's 

 boy en croupe. John Ruthven, of Kendal, was frequently engaged by 

 Sedgwick to collect fossils for him.^ The older rocks of North 



1 Sedgwick, T.G.S. fa) iv. 48; Proc. G. S. iv. 224; Phil. Mag. Ivi. 257. See 

 also Life of William Smith, p. 104. 



