128 DESCRIPTION OF THE STRATA. 



1. The alluvial covei'ing; 5 feet, 



2. Beds of sandstone; 50 feet. 



3. Shale, sandy and bitummous, with a few seams of sandstone : 

 30 feet. 



4. Sandstone, with a few seams of shale ; 25 feet. 



5. Dogger ; 5 or 6 feet. 



These beds bring us down to the alum works, which are carried 

 on in the next member of the series. 



6. Main bed of aluminous schistus, or alum rock; 200 feet. 



7. Imperfect seams, or flat nodules, of hai'd blue limestone, 

 mixed with alum shale ; 10 feet. 



8. Hard and compact alum shale ; 30 feet. 



9. Ironstone, in beds, or rows of nodules, interstratified with 

 the shale ; 15 feet. 



10. Shale, with a few ironstone nodules ; 40 feet. 



11. Beds of argillo-calcareous sandstone, with some shell lime- 

 stone, interstratified with seams of shale ; 60 feet. 



12. Alum shale ; 100 feet. This bed comes down to the beach, 

 where a hard blue shale, on which it rests, is washed by every return- 

 ing tide. — The shale that occurs below No. 8 is generally somewhat 

 sandy and micaceous, and of a coarser texture than the higher beds. 



By adding the numbers in the foregoing list of beds, it will be 

 found, that the height of the whole series has been estimated at about 

 570 feet, exclusive of the sloping bed on the beach. This estimation 

 falls a little short of the truth ; for the beacon on the heights near 

 Boulby (which Colonel Mudge calls Easington Heights) is 681 feet 

 above the level of the sea; and the difference of altitude, between 

 that beacon and the verge of the cliff in front of it, is much less than 

 100 feet. The beds, however, vary in thickness, in different places ; 

 though they are much more uniform in their nature and order than 

 those of the series last described. 



