Phi/sical Structure and older stratified Deposits of Devonshire. 687 



mantle round the central rock : yet the ends of these abutting strata are per- 

 fectly metamorphic. This fact we think important, as it proves to demonstra- 

 tion, that these strata are, in the strictest sense, metamorphic, and do not 

 belong-, as has been supposed, to a system of deposits older than the less cry- 

 stalline beds, which are further from the granite. 



5th. There have been two distinct regions of elevation in the country above 

 described ; one commencing in the great granitic mass of Dartmoor and ex- 

 tending- into Cornwall, — the other, nearly parallel to, and not far from, the 

 north coast of Devonshire. The compression of the central mass in North 

 Devon, by the elevation and protrusion of the rocks on these two lines, may 

 perhaps have been among the means which produced the contortions of the 

 great culm-trough. 



6th. Lastly, as a general conclusion from all the previous details, it appear.s 

 that the rocks of Devon and Cornwall belong to three periods of formation. 

 The oldest includes the various groups of slate rocks, and, at least, a part of 

 the associated traps. The ne\t includes the culm series, the upper division 

 of which contains fossils identical with those in the upper division of the true 

 coal measures. The granite belongs to the newest period ; but (on evidence 

 not discussed in this paper) probably assumed its present position among the 

 rocks above described, before the deposit of the new red sandstone. 



