382 
BCIRKTIiriC NEWS, 
SCIENTIFIC NEWS. 
Geological Society. 
Dec. -3d, I 613 . 
The President in the chair. ' 
ITe Right Honourable the Earl of Hardwicke, 
George Croker Fox, Esq. of Falmouth, 
William Stewart Rose, Esq. Palace Yard, 
Thomas P, Smith, Esq. of Stoke Newington, 
were severally elected members of the Society. 
A paper, intitled “ Memoranda relative to the Potphyritic 
Veins of St. Agnes, in Cornwall," by the Rev. J. J. Conybeare, 
M. G. S. was read. 
The veins described in this paper occur on the coast betw^een 
St. Agnes and Cligga point, traversing or lying on the surface 
of rocks of tortuous killas. The veins themselves vary in 
thickness from forty feet to half an inch. Their general cha- 
racter is porphyritic consisting of a base composed of minutely 
aggregated quartz, mica, talcite, and probably felspar, in which 
are imbedded grains and crystals of quartz, feldspar, chlorite, 
mica, and talcite, in small patches. Sometimes the porphy- 
ritic character is superseded by a more completely crystalline 
one, approaching to granite, and containing small veins of tin 
stone. Sometimes again the veins comsist of quartz and tour- 
maline, forming a rock very nearly resembling that of St. 
Roche, 
The killas adjacent to the veins is more crystalline than else- 
where, and sometimes is scarcely to be dislingni.shed from 
gneiss. Mr, Conybeare considers tlie veins and the rock in 
which they occur, to be of con tern por.aneous origin. 
A paper intitled “ a Description of some specimens from the 
neighbourhood of Cambridge," by Henry Wai burton. Esq. 
M. G. S.was read. 
I 
These 
