JONUS — OUTLlKlt OF UPl'KK ■I'HUTIAUY IKOiNSAND. 
layinL![ bolbro com})etont authorities for having their affinities deter- 
mined, and their charaetoi'istic markings described. 
Mr. Mitchell, in his notice in your July number, lightly j)laccs this 
deposit, as also that of Cautei'land Den, amongst the very lowermost 
of our Forfarshire sandstones. The localities as well as the fossils 
clearly iuiUcate this. 
ON THE OUTLIER OF UPPER TERTIARY IRONSAND 
ON THE NORTH DOWNS OP KENT. 
By T. Rupert Jones, Esq., F.G.S., Assistant-Secretary of the 
Geological Society of London. 
Having at times been asked questions about the " Fossiliferous 
Ironsands" of the North Downs, which Mr. Prestwich described in 
the Jom-nal of the Geological Society in 1858, vol. xiv., p. 322, &c., I 
find that some little diagram appears to be wanted by amateur geo- 
logists and general readers for the clearer demonstration of these 
sti-ata and their relations to the Chalk and the Drift. 
I beg, therefore, to offer you the accompanying diagram, illustrative 
of the relationship of the so-called " Kentish Crag," agreeable, I 
believe, to Mr. Prestwich's views of the subject, as given in his 
elaborate paper before mentioned. Having seen the ground at Len- 
ham and Charing, to which Mr. Prestwich refers, and at the latter of 
which places my friend Mr. W. Harris, F.G.S., had some sections 
specially made, I feel the greater satisfaction in bearing testimony to 
Mr. Prestwich's careful working out of the whole question. 
In the diagram you wdl see the whole known succession of these 
u-onsand deposits at A, where such outlines as those of Paddlesworth 
and Vigo-Hill may be supposed to be represented ; and partial rem- 
nants are seen at B, C, D, and E. At F and Fa may be discerned 
instances of sandpipes which have imbibed the ironsands before the 
changes at the surface led to the denudation of the ironsands off the 
chalk, and the wearing of the Chalk into furrows and cavities, leav- 
ing the clayish sands and gravel now known as " Drift," of which G 
I'epresents the lower and H the upper portion. 
The sandjDipes at Lenham, w^here the ironsand is found to be richly 
fossiliferous, are such as are seen at F in the diagi'am, the broken 
u'onstone having sunk gradually in with the sinking superincumbent 
beds as the cavity was slowly made in the Chalk, probably by the dis- 
solution of the latter by means of percolating water.* At I the 
* See Mr. Prcstwicli's account of the formation of Sandpipes in the Chalk, 
Jour. Geol. Soc, vol. xi., p. 6-1. 
