64 REPORT — 1841. 



Dr. Moore exhibited a collection of the fossils just discovered in some of the slate 

 rocks. 



Notice of a series of Specimens from Mr. Johnsons Granite Quarries, near 

 Prince Town, Dartmoor. By the Rev. Dr. Buckland, D.D., F.R.S. 



To the depth often or twenty feet the granite is more or less decomposed ; surface 

 granite of this kind has too frequently been employed, because it was cheapest ; and 

 the result is, that after a few years' exposure to a damp and foggy climate, as in the 

 case of the prisons on Dartmoor, the decomposing granite becomes like a spongy 

 mass, absorbing water continually, unless the walls constructed of it are externally 

 covered with Roman cement or tiles. This defect is inseparable from granite, which 

 is not quarried from a depth beyond the influence of decomposition. At the bottom 

 of the Foggin Tor quarries a mass of virgin granite is laid open to a great extent, 

 which is entirely free from this influence ; and from hence the beautiful granite is 

 obtained v.-hich is now in use for Lord Nelson's monument in Trafalgar Square. 

 Dr. Buckland also exhibited a mass of amethystine quartz, from Dartmoor. He 

 next described Earl Morley's quarries of potter's clay near Shaw, seven miles north 

 of Plymouth. Here the surface, over hundreds of acres, consists of decomposed 

 white felspar, which is purified by passing streams of water over it, and affords a fine 

 porcelain clay of unusual purity, from which ornamental figures, &c. may be made, 

 and which is largely exported to the potteries. Specimens of the decomposing fel- 

 spar, and the porcelain prepared from it, were exhibited by Dr. Buckland ; also fire- 

 bricks made from the same clay in its natural state, which resist a stronger heat 

 than Stourbridge bricks in the black bottle-glass furnaces. 



On analysis, the Morley clay gives only silica, alumina, and water. The decom- 

 posing granite of the Morley Clay Works closely resembles that near St. Austle in 

 Cornwall. Like the decomposed granite of Carcluse, near that town, it is also in 

 some parts abundantly traversed by minute veins and insulated crystals of tin ore. 



Dr. Buckland also exhibited water-pipes of a cheap kind, made from the coarser 

 strata of decomposed granite that accompany the tertiary brown-coal at Bovey Heath- 

 field, near Newton Bushell. 



Mr. Dawson exhibited a model of the Great Landslip of Axmouth, which took place 

 at Christmas, 1839. It was constructed on a scale of 120 feet to the inch, and repre- 

 sented a mile and a quarter. According to Mr. Dawson, the length of the chasm 

 caused by this subsidence was 1000 yards, the breadth 300 yards, and the depth 130 

 to 210 feet; 22 acres were sunk in the chasm. 



Mr. S. P. Pratt exhibited specimens, supposed to be from the slaty rocks over- 

 lying the limestone of Mount Batten ; they were derived from blocks lying on the 

 beach close to the black shales ; one piece was in contact with the bed containing 

 Encrinites. They contained several species of plants and scales of fish. 



Major Harding read a notice of the discovery of some fossils on Great Hangman 

 Hill, near Combemartin, North Devon. They consist of shells in the state of casts, 

 and appear in large detached and ferruginous masses of quartzose rock, ranged on the 

 surface. Major Harding has also observed a similar formation in the valley of rocks 

 near Linton. 



Mr. J. C. Bellamy exhibited a collection of Devonian fossils, containing about 

 150 species, and a printed table of genera, showing the various localities in which 

 they were obtained ; he stated the relative abundance of groups of fossils in these I'ocks, 

 as occurring in the following order : — Polypiaria, Crinoideaj Conchifera, Cephalopoda, 

 Gasteropoda, and Crustacea. 



Notice of the Heave of a Copper Lode. By J. Boswarra. 



On the Occurrence of some minute Fossil Crustaceans in Palceozoic Rocks. 

 By John Phillips, F.R.S., G.S. 



The freshwater limestones of Sussex and the tertiary beds have yielded great ahun- 



