1313. J Geological Society. 69 



On Jan. 15, a paper by Mr. Conybeare was read, on the 

 origin of a remarkable elass of organic impressions occurring in 

 nodules of flint. It consists of small round compressed bodies, 

 not exceeding the eighth of an inch in their longest diameter, 

 and connected by processes of the fineness of a hair. Mr. 

 Conybeare shows clearly that they occur between the bony plates 

 of a bivalve shell, the ostreo pennite of Welsh, and likewise in 

 another shell, probably belonging to the genus ostraea. He 

 conceives them to be casts of the cells of some minute parasitical 

 insect inhabiting the shells in question. 



On the 19th of Feb. a paper by John Taylor, Esq. was read, 

 on the economy of the mines of Cornwall and Devon. The 

 stannary laws are confined to the tin mines ; the copper mines 

 are left open to the agreement that may be made between the 

 proprietors of the soil and the mining company. In general, 

 the lord of the soil grants a lease for 21 years, subject to certain 

 regulations. The adventurers divide the whole concern into 

 sixty-four shares, which are divided among themselves and their 

 friends. The mines are wrought by the piece, and the working 

 disposed of by a kind of auction. The smelting companies for 

 copper have seldom any share in the mines. The copper is all 

 carried to Swansea, where it is smelted. 



On the 5th of March, two letters from Mr. Webster, 

 draughtsman, and Keeper of the Museum to the Society, were 

 read, giving an account of a calcareous strata of later formation 

 than chalk, and distinguished by containing fresh water shells, 

 discovered by him on the north side of the Jsle of Wight. He 

 thinks there are two fresh water formations, with a marine for- 

 mation between them. The lowest consists of beds of sand and 

 marl, with numerous fragments of the limnea of Lamark, and 

 two species of planorbis. The marine formation lying over it is 

 blue clay, with venuses, oysters, and various turbinated shells. 

 The upper fresh water formation consists of a calcareous rock, 

 inclosing numerous and very fine specimens of the limnea and 

 planorbis. 



A paper by Dr. Macculloch on the granite tors of Devonshire 

 and Cornwall was read. The granite in these counties is natu- 

 rally split into cubic fragments by perpendicular and horizontal 

 rents. These, by exposure to the weather, occasion the rock to 

 split into fragments, the edges of which are gradually rounded 

 of). Dr. Macculloch supposes that crystallization began in the 

 Centre of each of these cubic blocks, and extended on every 

 side till they met, but could not penetrate. By this hypothesis 

 M iCCOUDts foi the rents, and tor the greater hardness in the 

 centre of the blocks than at the circumference. 



On the 19th of March a paper was read on the rocks at Clo- 

 velly, in Devonshire, by the Rev. J.J. Conybeare. Theft* rocks 



