Geological Society. 567 



much altered, and encloses numerous small garnets. Remains of 

 plants are scarce, but impressions of Calamites have been found ; and 

 minute portions of vegetable matter occur in some of the beds of 

 sandstone. 



Transition System. — The culm measures rest unconformably on 

 a series of deposits belonging to this system, and divided by the 

 author into the following formations, in descending order : — 



1. Rag Limestone. — A calcareous rock, coarsely laminated, of a 

 dirty red colour, and abounding with stems of encrinites. Locality, 

 Forest of Denbury. 



2. Shale. 



3. Great Limestone. — ITiis is the limestone of Newton Bushel 

 and Torquay. It is distinctly jointed, the prevailing strike of the 

 joints being, for one set, N.N.W. to S.S.E., for the other, W.S.W. 

 to E.N.E.; but considerable variations are stated to occur in dif- 

 ferent quarries. 



Organic remains are very numerous, both corals and shells. At 

 its base the deposit presents several alternations of shale and black 

 limestone, and contains some peculiar fossil shells. It passes gra- 

 dually into the next formation. 



4. Argillaceous Slates and Sandstones, generally Red. — This de- 

 posit is of great thickness, forming the principal part of the slate- 

 hills, and is sometimes worked for roofing- slate. It contains bands 

 of limestone of a peculiar character. Organic remains occur only 

 in the upper part, and agree apparently with those of the " great 

 limestone." 



5 . Lowest Bmd of Limestone. — The limestone between Staper-hill 

 and Bickington, and on the highway road by Goodstone to Ashburton 

 and Buckfastleigh, is assigned to this portion ; also that of Chudleigh, 

 and the limestone at the base of Great Haldon is perhaps of the same 

 age. The organic remains consist of corals and shells. Thin seams 

 of carbonaceous matter also occur. 



Igneous Rocks. — These formations consist of granite, porphyry, 

 and trap. The granite of Dartmoor was shown in 1836, by Prof. 

 Sedgwick and Mr. Murchison, to be more recent than the carbonife- 

 rous strata ; and Mr. Austen adopts the same view, as veins of gra- 

 nite penetrate the culm beds at Higher Alway and Lower Alway, 

 neaj* Bovey. The principal mass of Devonshire granite has in some 

 places a height of 1800 feet, but over the whole of its area there is 

 not the sHghtest appearance of any stratified deposit. The granite 

 of Dartmoor is considered by Mr. Austen to be of different ages, 

 as veins of coarsely grained are intruded among the common variety. 

 Blocks of hornblendic granite are said also to occur, imbedded in 

 the true granite ; and in some places the granite is so felspathic as 

 to resemble trachyte. 



Trap Rocks — The author describes, with some detail, the horn- 

 blendic trap dyke of Wear, and shows that it must have been irrupted 

 subsequently to the deposition of the chalk, because fissures in the 

 limestone, traversed by the dyke, are filled with fragments of various 

 formations, including chalk, and are charged with manganese, an 



