GEOLOGY 
entirely. It may not be out of place to mention here that the present 
writer determined this point in the early ‘seventies,’ and officially re- 
ported the foregoing conclusion to the Director of the Geological Survey 
in May, 1874. 
As the Yoredale Rocks are of considerable commercial importance, 
some details regarding them are given here, as follows :— 
The highest beds are stated first ; and the local names, as employed 
in Alston Moor and elsewhere, are given in square brackets :— 
YoREDALE Rocks 
(1) Upper Section :— 
Thickness about 500 feet, strata very persistent. The sandstones and 
shales are not subject to the westerly thinning that affects rocks of 
this kind which belong to the Lower Section :— 
Sandstones and shales, with an important and very persistent coal 
seam [The Tanhill Seam] which ranges up to 4 feet in thick- 
ness. 
Shales with [The Fell Top] Limestones. 
Shale. 
Limestone [The Crag Limestone of Alston = the Crow Limestone 
and Chert of Yorkshire]. 
Sandstone (with two or more coals, locally worked) [The Fire- 
stone, Ten Fadom Grit]. 
Shale. 
Limestone [The Little Limestone = the Red Beds Limestone and 
Chert]. 
Coarse grits [The Coal Sills] with a very constant seam of coal [The 
Tindal Fell Seam] which ranges to 4 feet 6 inches, and is 
locally accompanied by other seams. These represent the 
Edge Coals of the Lothians (vide Gunn, Trans. Geol. Soc. Edin. 
vii. 367), the Lickar Coals of Northumberland, and shales and 
cherts. 
The foregoing strata represent the lower part of the Whitehaven 
Coal Measures. 
(2) Lower Section :— 
Total thickness ranging from 500 feet on the west of Cumberland, to 
1,200 on the east :— 
Limestone [The Main, Twelve Fadom, Dryburn, or Great Lime- 
stone]. 
Coal, sandstone, shale. 
[The Limestone Post = The Upper Undersett Limestone of north- 
west Yorkshire. | 
Coarse Grit [The Quarry Hazel of Alston]. 
Shales, thinning westward. 
Siliceous limestone (.e. containing organic silica, and not sand) [The 
Four Fadom, Low Dean, or Lower Undersett Limestone]. 
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