DAKYNS: GEOLOGY OF GRASSIXGTON AND WENSLEYDALE. 141 
sisting mainly of sandstone, and above these the limestone on which 
West Witton stands. This we identify with the Simonstone Lime- 
stone. Above it come measures consisting of shale and sandstone, 
the latter being particularly developed round the gable end between 
Bishopdale and Walden, where it lies immediately on the limestone. 
Above these measures comes the Middle Limestone. This limestone 
is between West Burton and West Witton far thicker than usual, 
being as much as 250 feet thick. It generally has a sandstone about 
10 feet thick at its base. The Middle Limestone is overlaid by a 
series of sandstones and shales with thin limestones. The sandstones 
generally predominate, but they thin away up Walden, and a little 
limestone overlying them swells out into a bed of respectable thick- 
ness, which entirely replaces the sandstone at Walden Head. The 
shales connected with these beds, and lying immediately above the 
Middle Limestone, are highly ferruginous. 
Above the Sandstone-Limestone Series come shales and then 
the Underset Limestone. This is a very variable bed in this part of 
the country ; it is sometimes absent altogether or too thin to be 
seen ; at other times it is an important rock nearly equal to the Main 
or Middle Limestones. It sometimes has a workable coal seam 
below it, and in the lower part of Walden there occurs above it a 
hard ganister-like sandstone with rootlets, which has been found 
useful for walling and other purposes. The limestone itself is some- 
times impure towards the top 
Over these beds come shales, and then the Main Limestone 
usually with a sandstone base. 
The limestone consists of two parts, a lower part of pure lime- 
stone, and a cherty part, above which come the sandstones and 
shales of the Millstone Grit Series. 
At or near the base of the Millstone Grit is a workable seam of 
coal, which has been got at Petticoat Rake, adjoining Fleensop. The 
coal was nine inches thick. It is not persistent, however, for it lies 
in " pools aud gutters " between " rigs of chert." It is in places three 
feet thick ; then deteriorates and " nips out." The cherty beds con- 
sist of dun limestone, grit and chert. 
The highest bed of Millstone Grit occurring west of the Cover 
13 
