of Devojishire and Cor mv oil. 121 



which appears to me to rise above this mountain plain, and which 

 is, without doubt, the highest point of all that part of the country, 

 is Craw-Mere rock, where the two rivers Oakment and Dart have 

 their source. 



I bent my course from Two Bridges to Launceston, by St. Mary 

 Tavy, Brentor, and Lifton, making a circuit of the exterior boundary 

 of that part of Dartmoor forest. As long as the mountain plain 

 continues, the country preserves the same appearance, and all along 

 the road between Two Bridges and Tavistock, for the first six or 

 seven miles, we find on the surface of the ground great numbers of 

 granite-blocks ; these probably come either from the tors, or are 

 produced by the rock on the surface splitting in that manner, in con- 

 sequence of the continued action of external agents. Several of 

 these blocks are so firmly fixed in the ground from which they pro- 

 ject, and are besides so uniformly spread over the surface in every 

 direction, that they cannot be supposed to have been transported 

 by a current to the place which they now occupy. 



At the distance of three miles and a quarter from Tavistock the 

 grauwacke begins to re-appear in a very distinct manner, and at 

 the height of one thousand one hundred and twenty-nine feet 

 above the level of the sea, which is rather considerable for this 

 formation. 



From this place, the country lowers with a pretty quick descent 

 towards Tavistock, and this change of rock is accompanied by so 

 complete a change in the vegetation, that it is impossible not to be 

 struck by it. Nothing can be more remarkable than to see on the 

 skirt of this mountain plain, towards St. Mary Tavy and Brentor, 

 highly cultivated vallies, succeeded by rich pastures, which rise as 

 high as the line of superposition of the secondary rocks, above 

 which there is nothing but bare and naked rock. 



