86 
THE GEOLOGIST. 
north side of Carlton, or, more properly, Dromonby Bank. In 
some pai-ts, it it is very abundant in organic remains, and contains 
whole rocks which are little else than a congeries of extinct molluscs 
the Grijphcea 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 di\isions 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 
rehquise, especially in Belemnites, O^hmridce, and Cardimn trimcatum, 
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 gTeat 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 ii^on." 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) 
Ironstone — main block 
12 
0 
(parting) 
Ironstone — bottom block, (variable) 
1 10 J 
Shale 
7 
Ironstone-band 
1 
Shale 
6 
Sandstone-band 
0 
10 J 
ft. 
ft. in. 
l32 6 
15 6 
The above gives a sohd 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 (y . 
Ironstone — good 1 Q 
