86 



THE GEOLOGIST. 



north side of Carlton, or, more properly, Dromonby Bank. In 

 some parts, it it is very abundant in organic remains, and contains 

 whole rocks which are little else than a congeries of extinct molluscs 

 the Gryphcea incurva being one of the most familiar and characteristic. 

 No part of the Lower Lias has ever in this district been wrought for 

 economic purposes. From this we proceed to one of the most im- 

 portant divisions in that respect, namely — 



c, The Ironstone or Marlstone Series. — The lower part of this series, 

 which we may estimate at a total of one hundred and fifty feet in 

 thickness, consists of alternations of shale, marlstone, and sandstone, 

 of a soft and argillaceous character, generally abundant in fossil 

 reliquiae, especially in Belemnites, Ophiuridce, and Gardium truncatum, 

 and partially ferruginous. A good section may be obtained at the 

 same points as I referred to in the last division, and the marlstones 

 may be well seen in the prominent edges which they form in the far- 

 famed Roseberry Topping, at the east end of the Wainstones Bank, 

 and many other elevations. 



It is, however, to the great ironstone-band, which forms the highest 

 stratum in this series, that this district owes all its celebrity as an 

 iron-producing country, and in respect of which we may truly say, 

 it is a " good land, and a land whose stones are iron." The seam 

 was first developed in 1848, in the picturesque hill of Eston Nab, 

 where the yield may be calculated at about fifty thousand tons to the 

 acre. The following detailed section is from a communication by 

 Mr. John Marley, C.E., to Professor Phillips:— 



ft. in. 



Ironstone — top block, left as roof ... 0 11 

 (parting) 



Ironstone — second block 2 3 



(parting) \-17 0 



Ironstone — main block 12 0 



(parting) 



Ironstone — bottom block, (variable) 1 10J 



Shale 7 0^ 



Ironstone-band 1 8 ( 



Shale 6 0C 



Sandstone-band 0 10 ) 



ft. in. 



15 



ft. in. 

 32 6 



Tlic above gives a solid mass of ironstone rock no less than seven- 

 teen feet in thickness ! This is, however, the point at which we find 

 its greatest development, since at Grosmont, near Whitby, the same 

 series is found in this altered and divided state : — 



ft, in. 



Shale 0 0 



Ironstone — " Pecten-seam," in two bands, separated 



by one feet six inches of shale 4 0 



Shale 4 0 



Ironstone — good 1 0 



