108 Dr. Berger on the physical Structure 



PfyfFer are, I believe, the first, who paid attention to this circum- 

 stance : Saussure in the mountains of Meillerie and St. Gingouph, 

 in Savoy, Pfyffer in the Alps bordering on Lucerne.* The neigh- 

 bourhood of Plymouth affords an example of it in this part of Eng- 

 land. 



As the physical structure of the western part of England, from the 

 banks of the Tamar as far as the Lands End, offers little variety in 

 geology, and as the great masses consist of a small number of dif- 

 ferent rocks, it will, I think, be convenient, to give, at first, a sketch 

 of the chain of mountains which traverses this part of the country, 

 such at least as I conceive it to be. It will be an outline, which 

 may afterwards be more easily filled up by future observations. Be- 

 sides, as the grauwacke constitutes one of the most essential com- 

 ponent parts of this chain of mountains, and as it is susceptible of 

 numberless modifications, it will be better to give, in the first place, 

 some details on the nature of this rock in the different states which 

 it assumes. 



General Observations on the low Mountain-chain of Cornwall. 



The chain of low mountains, which forms the county of Corn- 

 wall, extends nearly into the centre of Devonshire, comprehend- 

 ing the elevated and irregular mountain plain, called Dartmoor 

 Forest. 



Like all primitive chains, it stretches from N.E. to S.W. or, more 

 correctly, from E. N. E. to W. S. W. extending in this direction 

 from 115 to 118 miles. 



Its line of direction is pretty accurately represented by a line 

 passing through the following places, viz. Two Bridges, Launceston, 



» Voyages dans les Alpes, \ 325. 



