UPPER SHALE. 55 



The nodules and cakes of flint do not occur in the coloured 

 chalk, but only in the white; and in the latter they are most abundant 

 in the middle parts of the beds, being very scanty in the loose chalk 

 near the surface, and still more so in the lower part of the white chalk, 

 where it passes into the grey chalk. The flint is very plentiful among 

 the excavations at Flamborough Head. 



The flint, as well as the chalk, sometimes contains organic re- 

 mains. It may also be observed, that many of our nodules of flint, 

 when broken, exhibit a variety of colours, as yellow, orange, blue, 

 &c.: and these colours are sometimes disposed in concentric zones, 

 and sometimes in a clouded irregular form, not unlike the Egyptian 

 pebbles. 



The bed that immediately succeeds the chalk may be designated 



THE UPPER SHALE. 



A great variety of the beds i» our district come under the deno- 

 mination of shale, or scMstus. Some of these beds are bituminous, or 

 coaly; aome arenaceous, ov sandy; but a much greater number a>-§-27/a- 

 ceoMS or aluminous, containing a large proportion of clay. Their co- 

 lour varies according to their ingredients, th&coal shale being blackish, 

 the sandy shale light grey, and the elay shale usually dark grey. 

 The last two have sometimes a blueish tinge; and we may add, that 

 the clay shale is often found of a very dark colour, approaching to 

 black ; especially in the recent fracture. In some instances it is of a 

 pale grey colour; and very often, the exposed surface acquires a 

 ferruginous hue. The sandy shale is frequently micaceous, abounding 

 with specks of the shining substance called mica. These three kinds 

 of shale cannot always be correctly distinguished, as they often pass- 

 into one anotlier, and the diffei'ent qualities assigned to them may 

 sometimes be found blended together in the same bed. All the beds- 



