SECOND SHALE. 87 



amoiig^ the strata in Stainton Dale cliffs, and other places, it is so 

 much of a piece with the other numeraus shale beds, alternating with 

 the sandstone in a lower part of the strata, that it can scarcely be 

 identified; except where we can distinctly observe the beds that im- 

 mediately succeed it. 



This shale, which occupies so large a space in our strata, is far 

 from being uniform in its qualities. In many places, it differs little 

 from the upper shale; containing a large proportion of clay, with a 

 mixture of calcareous matter. In others, it is sandy and micaceous; 

 and indeed there are few places where we do not find in it small 

 shining specks of mica. Its general colour is a blueish grey; some- 

 times very light, sometimes so dark as to appear almost black, but 

 commonly of an intermediate hue. In some places too, it is of a dull 

 ash grey or dusky colour, especially where it partakes very largely 

 of clay, as in some of tlie lower parts of the Gristhorp cliffs. In a 

 part of the slope below Whitestone cliff, a little above a free-stone 

 quarry, we find some greenish shale, which seems to be the lower 

 part of the same shale that appears in the front of the cliff. The 

 slvale is generally most sandy, Avhere it is about to pass into sand- 

 stone, and where it contains most sandstone beds ; and yet at the 

 point east from Cayton mill, where, as was stated, the sandstone 

 tliickens, and the shale is compressed, the compressed bed is so 

 highly argillaceous, that we find on its surface an efflorescence of 

 sulphate of alumine, or native alum, as well as some sulphate of iron. 

 The same phenomenon may be seen in a few other spots, particularly 

 near the White Nab, on the other side of Cayton, where a portion of 

 the shale is uncovered. 



The sulphur in these native preparations is derived from the de- 

 composition of pyrites, which is found in several parts of this shale ; 

 sometimes in clusters of elegant crystals, like those in the Lower 

 chalk. Oxide of iron is also very common in many parts of the 



