SPENCER : THE YOKEDALE AND MILLSTONE GRIT ROCKS. 385 
then runs up to Crow Hill in Sowerby and forwards through the 
moorlands of Manshead ; then crossing the Ryburn, where the 
Kinder Grit comes to the surface, it proceeds up the eastern side of 
Black Castle water to Blackstone Edge (1,550 feet above sea level), 
thence over the Yoredale outcrop and the anticlinal fault and 
the Third Grits to the outcrop of the Lancashire coal strata, 
^bout two miles east of Littleborough. The length of country 
<jovered by the section is about 11 miles, in a north-east and 
•south-west direction. The dip of the strata is also in a north- 
easterly direction. From the anticlinal axis down to the river 
Calder the average dip between the two places is about 200 feet 
per mile, or one yard of fall for every 26 yards. From the 
Calder to Ringby Hill, north of Halifax, in the line of the section, 
the dip is 160 feet per mile, or one yard in every 33 yards. 
The dip of the strata in Shibdendale is also to the north-east. 
The dip or inclination of the strata is very interesting to 
the geologist, and must be taken into account in all our calcula- 
tions concerning the thickness of the various strata, (fee. It 
is also very important that measurements of these dips should 
be taken not merely in one direction but in several, and not 
only for a limited distance but for many miles in length, before 
our deductions from them can be relied upon. A section of the 
strata taken from Black Hambledon to the Fly quarries (Oxenhope), 
a distance of eight miles (direct west and east), gives us a fall 
•of one yard in 41, and from Oxenhope Moor, via Halifax, to 
Elland the Rough Rock falls from 1,450 feet in the former place 
to about 250 feet in the latter, which gives a fall of 1,200 feet, 
or 150 feet per mile, or one yard in 39. From these calculations 
it will be seen that the old notion of a dip of one yard in 20 
is not correct when the dip is taken over several miles in extent, 
^il though in a few places it may be applicable ; in fact, dips to 
any amount from vertical 70°, 45°, 40°, 221°, 15°^ 12°, 5°, down 
to a dead level, occur locally in connection with faults. It will 
be seen from Section I. that the hilly country through which that 
section runs, and also that to the north-west of it, really form 
part of the Pennine Chain, because their strata are all affected by 
