*J70 Geological Society. 



June 5, 1838. — Read observations on the Spongilla fiuviatilis. 

 By John Hogg, Esq., M.A., F.L.S. 



Read also a paper, entitled, on the Number and Structure of the 

 Mammulae employed by Spiders in the process of Spinning. By 

 John Blackwall. Esq.. F.L.S. 



Mr. Saunders, F.L.S., presented specimen?, oiPotamogeton planta- 

 gineiis and Mendicago denticulata, var. apiculata, gathered in Sussex. 



Mr. Hogg, F.L.S., exhibited specimens oi Plumatella repens and 

 Spongilla fluviatilis from a rivulet near Norton in the county of Dur- 

 ham. One of the Spongilla was attached to the larva-case oi Phry- 

 ganea, and another to a tuft of Hypnum riparium, which it had en- 

 tirely enveloped. 



June 19, 1S38. — Specimens of the tree which yields the Caout- 

 chouc or India Rubber of Commerce, and which proves to be a spe- 

 cies of Hevea, nearly related to the guianensis of Aublet, were pre- 

 sented by Sir Everard Home, Bart., Capt. R.N. 



Read a Description of a new species of Cattleya. By Mr. Robert 

 H. Schomburgk. Communicated by the Secretary. 



Read likewise observations on some genera of Plants connected 

 with the Flora of Guiana. By George Bentham, Esq., F.L.S. 



Nov. 6, 1838. — Read a letter from Mr. Jonathan Couch, F.L.S.. 

 giving an account of a single specimen of Wilson's Petrel {Procel- 

 laria Wilsoni) having been found dead in a field near Polperro in 

 Cornwall, about the middle of August last, at a time when the 

 Stormy Petrel (P. pelagica) abounded on the coast, most probably 

 driven thither by the state of the weather at that period. 



Read also Observations on the Cause of Ergot. By Mr. John 

 Smith, A.L.S. 



The Chairman announced to the Meeting that the late Nathaniel 

 John Winch, Esq., of Newcastle-upon-Tyne, had bequeathed to the 

 Society liis entire Herbarium, consisting of upwards of 12,000 spe- 

 cies of plants, together with his library of Natural History. 



November 20, 1838. — Read the Description of a new Genus of 

 Plants belonging to the Natural Family Bignoniacea. By Professor 

 Don, Libr. L.S. 



There was also read an account of a new species of Lepidosperma. 

 By Dr. John Lhotsky. 



GEOLOGICAL SOCIETY. 



Feb. 6. — A paper " On a probable Cause of certain Earth- 

 quakes," by M. Louis Albert Necker, For. Mem. G. S., was read. 



The object of this memoir is to show, that some earthquakes may 

 be due to the falling in of the roof of cavities, produced by the sol- 

 vent or erosive powers of subterranean bodies of water on beds 

 and masses of gypsum, rock salt, limestone, marl, clay or sand. 



M. Necker was induced to enter upon the inquiry in conse- 

 quence of the earthquake which desolated, in 1829, a considerable 

 part of the country on the banks of the Segura, in Murcia, having 

 occurred in a district, which is stated to contain no volcanic or trap- 

 pean rocks ; and because the event was unaccompanied by any of 



