60 
DESCRIPTION OF THE ROCKS 
The fact already established of the attenuation of the whole Yore- 
dale series, in a south-eastward direction, now becomes important. We 
have seen how the Yoredale rocks were reduced in thickness from 
Hawes to Great Whernside. As there can be no doubt of the con- 
tinuity of the upper part of the great limestone masses of Whernside, 
Lofthouse, and Grassington, we are forced to admit that the pebbly 
gritstone which lies over the Parkhead limestone at Kettlewell is 
identical with that of Lofthouse, and this with the lower grits of 
Greenhow and Grassington. It is already proved to a certainty that 
the Parkhead limestone is the main or twelve fathom limestone of 
Swaledale, Yoredale, Wharnside, Ingleborough, and Penyghent. It 
follows that the pebbly grit (bearing grit) of Nidderdale, like the 
‘ millstone grit’ of Ingleborough, is above the main limestone, and fat 
below the ‘ millstone grit of Brimham,’ 
What, then, is the relation of the Nidderdale millstone grit to the 
Ingleborough grit ; both being certainly proved to be not far above the 
uiain limestone? To those geologists who are not practically versed in 
the variations of sedimentary rocks, this question may appear of easy so- 
lution. It is nevertheless replete with embarrassment. For as all the 
terms of the Yoredale series, previously discussed, vary with locality, 
and as all the terms of this millstone grit series, coal, shale, grit, and 
limestone, are still more variable, and according to different laws, which 
refer to different local centres, and as finally the Ingleborough grit lies 
very much in distant outliers, I have hesitated long before fixing 
my opinion. 
Parting from Ingleborough, where this grit forms the very summit 
of the mountain, we find in Penyghent the very same limestone series 
surmounted by the same millstone grit, and on this a considerable 
thickness of shales and grits yielding coal. In Fountains fell also, 
the same grit occurs, hut thinner, under the same coal shales and grits 
as in Penyghent. A similar but less complete section in Coska, con- 
ducts us to the ridge between Littondale and Langsterdale, which 
consists of those grit rocks and shales lying over the main limestone. 
