‘Trap on the 
North Bank of 
the Tees. 
154 Professor Sepawick on the 
them would lead me into details quite foreign to the objects of this 
Paper. Among the most remarkable may be mentioned the two 
following : 
(1.) A vein which cuts through the escarpment of the trap 
(the great Whin Sill) and forms a great ravine near the village of 
Holwick. From thence it crosses the bed of the river and ranges 
through the hill immediately behind Middleton. 
(2.) A great vein, or system of veins, which ranges across the 
river, in a direction N.N.W. and S.S.E., about two hundred yards 
below Holwick Head. It has been traced through a considerable 
extent of country, especially on the south side of the Tees; and 
all the beds on the N.E. side of its course are thrown up above 
their proper level*. 
II. 1 now proceed to consider the manner in which masses 
of trap are associated with the other strata in certain parts of High 
Teesdale. 
(1.) In a Paper which was read to the Society in 1822, I de- 
scribed a mass of trap, which occupies the left bank of the Tees, 
nearly opposite to the entrance of the Lune; and extends about 
a quarter of a mile to a high bank called Foggerthwaite, where it 
is seen abutting against a bed of slate clayt. 
* Where this vein intersects the great /Vhin Sill, it contains much sulphate of barytes, but 
does not appear to be metalliferous. 
Though the great metalliferous veins of Teesdale intersect, indifferently, all the strata of 
the district, yet they are by no means equally rich in all parts of their course. Some particular 
parts of the formation are eminently productive (as for example, almost all the beds from 
No. 6. to No. 27. of the general section); but the great Whin Sill is not commonly regarded as 
one of the bearing beds. To this rule there are, however, some exceptions, for productive lead- 
veins have, near the top of High Teesdale, been worked in the Whin Sill. In one or two parts 
of High Teesdale, I have seen minute veins, containing sulphate of barytes and smal] cubes 
of galena, passing through the trap. 
+ This mass of trap is of considerably greater extent than I supposed when I wrote my 
former paper (supra, p. 24.) Inthe same part of the paper Eglestone bank is erroneously 
written for Foggerthwaite bank. 
