188 DAVIS : SECTIONS IN THE LIASSIC AND OOLITIC ROCKS OF YORKSHIRE. 
of the cliffs at the east side of the Fault. On the west side of the 
Fault these shales are constantly exposed, especially at the great 
works, long since abandoned, at Peak and Brow. At Howedale the 
entire series may be examined and measured. Other small exposures 
occur in the neighbourhood : from Maw Wyke to Whitby the base 
of the cliff and the scars consist of this portion of the Upper Lias. 
The manufacture of alum was some years ago a large industry. 
The shales of this neighbourhood were the only source of alum, and 
though the disadvantage of want of fuel was great, the trade flourished. 
About 45 years ago a process was discovered by which a great pro- 
portion could be extracted from coal shale, and since then the 
ammoniacal liquor from the manufacture of gas has been utilized, 
and the Whitby alum was driven out of the field. The alum made in 
this district was potash alum, and it was manufactured as follows. 
The shale was first calcined, this was done by placing about 4 feet of 
shale over brushwood, setting it on fire, and repeatedly adding shale, 
the temperature being regulated so that the sulphur was not sublim- 
ated. This operation lasted oue or two years. The calcining floors 
may be seen at any of the old works. The calcined shale was then 
washed and the aluminium sulphate dissolved out. This was done in 
a series of cisterns, and the liquid was conveyed to the boiling house, 
the shale being now thrown aside in heaps. The liquor was evapor- 
ated, the potash sulphate or chloride added, which precipitated the 
alum. This was again dissolved in boiling water, and crystallized out 
in the form known to commerce. 
The fauna of the Alum Shales is even more rich than that of the 
jet rocks in large Saurians ; they are abundant both in species and 
numbers, and are the largest known. In addition to the Ichthy- 
saurians and Plesiosaurians there are the Teleosaurians. In the Lias 
of Lyme Regis and the South of England the Saurians come from the 
lower beds of the Lias, but in Yorkshire they occur in the upper beds. 
The profusion of Ammonites and Belemnites is greater in these beds 
than in any others, though the number and variety of the species is 
not so great. 
Above the Alum Shale, Tate and Blake consider that a series of 
shales form a passage bed to the Dogger Oolites. These authors 
