Culiri' and Plant-hearing Beds of Devon and Cofirsoall. 295 



and from the culm-field to the granite of Caradon Down* 

 N, and S. of the parallel of Launceston, we have constant 

 and repeated alternations, on a great and small scale, of 

 Cornish clay slate or killas, lenticular limestones, carbonaceous 

 slateSjCoddon Hill grits, and floriferous shales and sandstones; 

 while on the east of Dartmoor, at Doddiscomb Leigh, five 

 miles north of Chudleigh, we discover the Possidonia lime- 

 stones underlying a long series of alternations extending to 

 the mouth of the Dart, severally occupying miles of surface 

 on the maps, oftener so minute that they cannot be correctly 

 represented there at all. A cross section of this long line of 

 country exhibits repeated interchanges, at reciprocally vary- 

 ing levels of the Floriferous, Coddon Hill grits, coral lime- 

 stones, Cornish killas, conformable and unconformable trap- 

 rocks, and volcanic ash and grit, each and all, except the 

 Elvans, characterized hy plafiis, glancejlakes of anthracite, and 

 carbonaceous matter ; the limestones, with the exception of 

 the included carbonaceous beds and clay slate, being masses 

 of coral architecture, of which, from the many that have been 

 submitted to him, Mr. Lonsdale pronounces that not one 

 is a mountain limestone species. In other localities, both in the 

 slate and limestone, we have chambered and bivalve testacea, 

 almost none of which (except certain ones from the Plymouth 

 limestone, which is higher up in the series) are of carboni- 

 ferous species ; some of the Pethernwin and Landlake fossils 

 being identical with certain ones from the Trilobite slates of 

 Exmoor, others probably belonging to an independent forma- 

 tion not yet determined. 



We hope soon, however, to learn more on this head from 

 the critical knowledge of Prof. Phillips, Mr. Sowerby, and 

 Mr. Lonsdale ; but I know enough now to assert, without 

 doubt or hesitation, that the Possidonia limestones and the 

 plant- and culm-bearing series of Devon and Cornwall, is a 

 jperfectlij independent formation far below the carboniferous 

 limestone and its coalfield. This is all 1 have ever contended 

 for ; and as at length I am left to fight the battle single-handed, 

 and feel my confidence in the stern facts of Devon and Corn- 

 wall augment with the falling away of the support which 

 hitherto encouraged me, I fearlessly challenge the banded 

 world of geologists to disprove it. 

 Bleadon, near Cross, Sept. 9, 1839. 



As Mr. Weaver appears to assign no more than a fair value 

 to mineralogical character, and states that " a practical man 

 does not so readily conceive that a glossy clay slate, &c. can 

 be the equivalent of the Old Red Sandstone formation," &c., 

 I would ask him what mineralogical affinity even he could 

 possibly discover in the Coddon Hill grit layers, and the mill- 



