in Yorkshire and Durham. 215 
Egglestone, is about forty feet wide, and cuts through a bed 
of coarse grit, provincially called firestone. ‘The latter is about 
' sixty feet wide, and is associated with gritstone and a band 
of indurated shale which has been much quarried for whet- 
stones. 
It would certainly be very interesting to trace these dykes 
as far as possible through the eastern moors, as there can be 
little doubt of their connexion with some of those masses of 
trap which traverse the great coal-field. My own observa- 
tions were much too limited to complete this task. I however 
found on Woolly Hills, in the Woodland Fells, several quarries 
opened in a dyke which, from its position as well as in its 
structure, seemed to form a connecting link between the trap 
of High Teesdale and some of the dykes which traverse the 
country near Cockfield Fell *. 
Cockfield Fell Dyke. 
Proceeding some miles further to the S.E. we come to the 
north-western termination of Cockfield Fell dyke, which is 
seen in a quarry by the side of the brook which runs past 
Gaundlass Mill. In that single locality it assumes a compound 
form, being made up of three distinct and nearly vertical masses 
of trap alternating with a variety of indurated slate-clay. The 
following is a transverse horizontal section of the whole dyke. 
(1) On the south-west side, common coal shale, which, as it 
approaches the dyke, becomes much indurated and has a ver- 
tical cleavage. In this state it is provincially termed penczl. 
(2) Trap one yard. (3) Pencil about four or five yards, but 
of variable thickness and much shattered. (4) ‘Trap two yards. 
(5) Pencil half a yard. (6) Trap about seven yards. (7) 
Coal shale resembling No.(1). ‘These entangled masses of 
coal shale are probably not prolonged far beyond the quarry, 
as they are seen in no other section. 
The dyke afterwards ranges through the coal works which 
are opened in Cockfield Fell about half a mile to the north of 
* It is stated by Mr. Winch (Geological Transactions, vol. iv. p. 76.), that 
“at Egelestone, three miles below Middleton, a very strong vein of basalt 
may be seen crossing the Tees in a diagonal direction.” I suspect that he 
here alludes to the mass of basalt abovementioned, which appears on the 
left bank of the Tees opposite to the entrance of the Lune, as I in vain en- 
deavoured to discover the traces of a dyke further down the river. If this 
conjecture be right, it will be necessary to remove the dyke (which in the 
map accompanying Mr. Winch’s memoir is made to cross the Tees below 
Egglestone) to a place considerably to the N.W. ofits present position. 
hen so represented, it will be seen, by an inspection of the map, that the 
basalt in Teesdale and the neighbourhood of Cockfield Fell are much more 
nearly in a straight line than they haye been represented. h 
the 
