Mr. Winch on the Eastern Part of Yorkshire. 549 
mg to situation, or, in other words, forms a basin. Towards the 
north, the dip is to the south-west ; but at Coxwold, to the east. 
The thickness of the coal varies from 6 or 7 to 14 inches, but, 
to use the pitman’s phrase, is frequently nipped out; the beds of 
sandstone meeting, and not leaving a vestige of the coal. In the 
swellies the seam is thickest, and best in quality. This stratum, 
with its accompanying thil, when it does occur, is situated between 
the white or grey post and the white freestone, the former of which 
is about 11 foot, and the latter 21 feet thick. This thin coal for- 
mation upon the alum-shale undulates with the surface, which is 
not the case in the Newcastle coal field. 
A bed called the dogger rests upon the alum rock. It is a hard 
sandstone, containing a considerable quantity of iron. Its thickness 
is from 7 to 13 feet, and colour a dark grey iron-grey, containing 
rounded pebbles of the same substance, together with numerous 
small grains of shining smoke-grey quartz, and specks of white 
disintegrated felspar. Ammonites, belemnites, and trigonia clavel- 
lata, are occasionally imbedded in it. 
To this succeeds the enormous bed of alum-shale, from which 
alum has been manufactured ever since the days of Queen 
Elizabeth. The depth to which this stratum reaches has never 
been ascertained ; but to give an idea of its thickness, I need only 
mention that the cliffs at Bowlby are 600 feet high, 400 of the 
lower part being an entire mass of shale : and to what depth it 
may descend below the level of the sea remains to be proved. 
The upper part of the stratum of alum-shale is less compact than 
the lower, and containing a greater quantity of pyrites, produces 
more alum. Its colour is iron-grey ; and as large heaps continue 
to burn till the whole mass is reduced to reddish-grey ashes, when 
