1819.] Geological Society 221 
mene 
taking the observation also, and the position of ‘the ship’s head, 
modify the variation. The variation is likewise atlected by the 
. temperature, density, and humidity of the atmosphere. The 
direction of the wind and the dip were hkewise found to irregu- 
larly influence the variation. 
Feb. 18.—A paper, by Capt. E. Sabine, was read on the same 
subject. It was entitled “‘ The Irregularities observed in the 
Direction of the Compass Needles of H. M.S. Isabella and Alex- 
ander, in the late Voyage of Discovery, caused by the Iron 
contained in them.” 
LINNEAN SOCIETY. 
Jan. 26.—Mr. Smith’s paper, on the Botany of Jersey, Guern- 
sey, Alderney, and Sark, was concluded. | 
Feb. 2.—A paper, by Mr. John Lindley, entitled, “‘ A Mono- 
graph of the Genus Rosa,” was commenced. 
eb. 16.—The same paper was continued. 
GEOLOGICAL SOCIETY. 
Dec. 18.—A communication was read from Thomas Robinson, 
Esq. of Morley Park Iron Works, near Belper, Derbyshire, on a 
tree, apparently oak, found in these works. 
As the miners were sinking a pit for the purpose of obtaining 
iron ore, they discovered a tree, apparently oak, in an erect posi- 
tion, its bottom standing below the third measure of iron stone ; 
its length was about six feet; and its diameter 10 to 14 inches ; 
and its substance dark coloured and mouldering;; its position, and 
the unbroken appearance of the beds it traversed, seem to coun- 
tenance an idea, that it grew there previously to the deposition 
of the beds surrounding it. 
A communication was received from the Rev. William Buck- 
land, B.D. F.R.S. V.P.G.S. and Reader in Geology and 
Mineralogy in the University of Oxford, and the Rev. W. D. 
Conybeare, A.M. M.G.S. “ On the Geological Structure of the 
South Western Coal District, and on the Relations of the Depo- 
sites by which it is partially covered.” 
Jan.1, 1819.—The reading of Mr. Buckland’s paper, on the 
South Western Coal District, was concluded. 
This paper is understood to be introductory to a series of 
communications on this district, which appears generally to con- 
sist of two principal formations. 
The first reposes on the transition rocks, and includes the 
independent coal formation of the Wernerian school. 
The second consists of more recent horizontal deposites, lying 
unconformably on the transverse edges of the first formation, and 
partially filling the valleys and low grounds between the ridges 
constituted by them. 
The first formation consists of the following beds, beginning 
with the lowest. 
1. Beds of transition limestone and imperfect slate which the 
