Discrepancies 
in the Sections. 
Great ‘l'eesdale 
“ault. 
148 Professor Sepewick on the 
For these two sections, I am indebted to Mr. Walton, 
a mine agent at Middleton, in Teesdale. It may, perhaps, not 
be improper to add, that the word sill is synonymous with 
stratum—that plate designates all varieties of slate clay—that 
grey beds are composed of slate clay and siliceous grit—that 
hazle and firestone designate varieties of siliceous grit. The 
different slate sills are composed of fine schistose varieties of 
siliceous grit, which are sometimes used for roofing-slate. The 
coal sills of the district are principally composed of carbona- 
ceous shale, with a few thin layers of impure coal, much im- 
pregnated with sulphur. Connected with this subject, see 
Forster’s Section of the Strata from Newcastle upon Tyne to Cross 
Fell, and Transactions of the Geological Society, Vol. [V. p. 63—66. 
It will be seen (by comparing the first section, from No. 1. 
to No. 21, with the second section, from No. 4. to No. 27.) how 
difficult it is to identify all the subordinate parts of the forma- 
tion, even in the same district. In addition to the faults and 
dislocations, which throw great difficulties in the way of 
a correct comparison of the successive strata; the beds of grit 
and shale perpetually change their characters, and often replace 
each other. The beds of limestone are, on the whole, more — 
regular and continuous; and it is to their presence that all of 
the transverse vallies above described, owe their most remark- 
able features *. 
On commencing an examination of High Teesdale near Egle- 
stone Bridge, we soon discover that want of correspondence in the 
strata on the opposite sides of the river, to which I before alluded. 
* The elaborate section of the strata from Neweastle upon Tyne to Cross Fell, 
published by Mr. Westgarth Forster, is, Tf believe, partly compiled from various registers 
of the Lead-works which are conducted on Aldstone Moor, and in the higher parts of 
Weardale. For the purpose of further explaining the true relations of the great Whin 
Sill, to the inferior or superior strata, I will subjoin a short extract from that Section. 
EXTRACT 
