482 Geological Society. 
of America, and they know nothing of their family prior 
to the great- grandmother of the hoy, whose powers of cal- 
culatign have attracted so much attention and been éxhi- 
bited in this country. 
In consequence of the Christmas holidays and public 
thanksgiving, the Society then adjourned till Thursday, 
Jan. 21, 
GEOLOGICAL SOCIETY, 
Dec. 3.—The President in the chair, 
The Right Hon, the Earl of Hardwicke, 
George Croker Fox, Esq. of Falmouth, 
William Stewart Rose, Esq. Palace-yard, 
Thomas P. Smith, Esq. of Stoke Newington, were se- 
verally elected Members of the Society. 
A paper entitled ‘* Memoranda relative to the Porphyritic 
Veins of St. Agnes in Cornwall,” by the Rev. J. J. Cony- 
beare, M.G. S. was read. ‘ 
Phe veins described in this paper occur on the coast be- 
tween St. Agnes and Cligsa Point, traversing or lying on 
the surface of rocks of tortuous killas. The veins them- 
selves vary in thickness from forty feet to half an inch. 
Ther Beart character 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, felspar, chlorite, mica, and talcite in small patches, 
Sometimes the porphyritic character 1s superseded by a 
more completely crystalline one, approaching to granite and 
containing small veins of tin-stone. Sometimes again the 
veins consist of quartz and tourmalines, forming a rock very 
nearly resembling that of St. Roche. 
The killas adjacent to the veins is more crystalline than 
elsewhere, and sometimes is scarcely to be distinguished 
from gneiss. Mr. Conybeare considers the veins and the 
rock in which they occur to be of cotemporaneous origin. 
A paper entitled ¢ A Description of some specimens from 
the neighbourhood of Cambridge,” by Hen, Warburton, 
Esq. M, G. S. was read. 
These specimens formed part of a bed of rubble, covering 
the summit of a hillock of gray or the lower chalk, ahout 
five miles S.W. of Cambridge. This hillock, like several 
others in the same county, 1s situated. to the west of the 
great range of chalk, being surraunded by tne blue marl or 
gault, as it is provincially termed, from which the overlying 
bed of chalk is separated by a thin bed of green sand. The 
rubble, besides consisting of chalk and flint, also eon 
shel 
