ALUM SHALE. 143 



they are subject to considerable variations, in regard to their qualities, 

 and the spaces which they severally occupy. Sometimes the upper 

 part of the main bed of shale is sandy and micaceous, like the lowest 

 shale. This is especially the case, where the dogger is either wanting, 

 or materially changed ; as in the top of Kirkby alum works, where the 

 shale acquires a greenish hue to the depth of about 10 feet; and still 

 more, at the spot where the alum shale first rises above the sea, a 

 little to the south of Peak. There the dogger and the shale, where 

 they come in contact, seem to have mutually exchanged some of their 

 respective qualities ; the dogger acquiring something of the softness 

 and colour of the shale ,• while the shale, to a considerable depth, is 

 sandy and micaceous like the dogger, and of a lighter grey than is 

 usual in this bed. The shale partakes also with the dogger, in its 

 ferruginous and calcareous matter ; the latter being in some places so 

 copious that the shale effervesces strongly Avith acids. 



But the variations in this^series are most observable, in the hard 

 bands of limestone, ironstone, and sandstone, that run in the shale. 

 In some places, as has been intimated, the Sandsend or lias band is 

 contracted ; in others, it is dilated : and the same remark applies still 

 more to the Kettleness or ironstone band. The latter sometimes de- 

 scends towards the vStaiths or sandstone band; which is equally 

 subject to variations, the two or three thick beds, of which it is 

 principally composed, being in some places almost in contact with 

 each other, while in other places they widely diverge, considerable 

 beds of shale intervening between them. Illustrations of these re- 

 marks may be seen between Hawsker Bottoms and Robin Hood's 

 Bay ; and in the lower part of the hill at Kirkby alum works, as also 

 in some others of the Cleveland hills. 



Having taken a view of the beds composing this series, let us 

 now attend to the most remarkable breaks or dislocations in the alum 

 hills, and the principal undulations in their strata. 



