216 Proceedings of the Royal Physical Society. 
YOREDALE SERIES. 
/ 
Typical Area.—The rocks so named in the Valley of the 
Yore, by the late Professor Phillips. 
The Yoredale Rocks consist of alternations of shales and 
sandstones, with several thick beds of pure marine limestone. 
In the typical area the thickness is about 2000 feet. 
The rocks referred to this horizon in North Stafford- 
shire attain a thickness of 3100 feet while in South 
Lancashire it has a thickness of 2000 to 4000 feet.” 
. Mountain LIMESTONE. 
Calciferous Sandstone Series of Scotland. 
The Mountain Limestone is typically developed in the 
mountainous districts of North-West Yorkshire and the 
adjoining parts of Westmoreland. Here it consistsof a vast 
thickness of marine limestone, generally characterised by 
singular purity of composition. Traced towards the north- 
west, it is found that these limestones become more and 
more split up by shales, and then, as the rocks are}followed 
still farther to the north-west and the north, they are also 
split up by sandstones. The limestones concurrently become 
less pure and thin out successively from the bottom upwards, 
We therefore find in Northumberland the Mountain Lime- 
stone represented by a thick series of alternating*ishales, 
sandstones, and thin coals, among which the Limestones 
occupy a subordinate place, and are chiefly confined, to,the 
upper part of the series. 
The rocks here have assumed the Calciferous Sandstone 
Series facies, and as such have long been recognised.® 
At the meeting of the British Association at Birmingham 
1 Hull, Coal Fields of Great Britain, 4th edition, 1881, p. 184, 
2 Tbid., p. 199. 
3 The earliest published suggestion, as far as I am aware, that the Moun- 
tain Limestone was of the same age as the Calciferous Sandstone Series of 
Scotland, is given by Mr J. G. Goodchild, in a paper entitled Note on the 
Carboniferous Conglomerates of the Eastern Part of the Basin of the Eden— 
Quart. Jour. Geol. Soc., vol. xxx., 1874, p. 399. ; 
