Chalk and Oolites . Sect. V. Iron Sand,

139

The ochre of Shotovcr hill occupies a similar geologicalposition; a list of the accompanying strata will be found in theappended note.*

The workings for iron in the Weald of Sussex are describedin the agricultural survey for that eounty 3 from which anextract will also be found below.+

In these works they seldom undermine the ground, but as they dig awaythe earth below, others are employed to dig and carry off the surface;otherwise, the matter above, being of so light and flitting a nature, wouldfall in and endanger the workmen; for, as was observed before, the stra-tum of sandstone which occurs before they come to the fullers’ earth, doesnot lie, as in coal-pits, immediately over the matter they dig for, like aceiling, but even in the midst of the superjacent strata of sand, and there-fore can be no security to them if they undermine them.

The perpendicular fissures are frequent, and the earth in the strata,besides its apparent distinction into layers, like all other kinds of matter,by reason of its peculiar unctuousness, or the running of the adjacent sandimperceptibly among it, breaks itself into pieces of all angles and sizes.

For the geographical situation of these pits, they are digged in thatridge of sand-hills by Woburn; which near Oxford is called Shotover; onwhich lies Newmarket heath by Cambridge, and which extends itself fromeast to west, every where, at about the distance of eight or ten miles fromthe Chiltern hills , which in Cambridgeshire are called Gog-Magog; in Bucksand Oxon , the Chiltern hills , from the chalky matter of which they chieflyconsist; which two ridges you always pass, in going from London into thenorth, north-east, or north-west counties in the manner before mentioned :after which you come into that vast vale, which makes the greater part ofthe midland counties of Cambridge, Bedford, Bucks, Northampton, Oxford,and Gloucester, and in which are the rivers Cam, Ouse, Nen, Avon, Isis,and others, which I take notice of because it confirms what you say ofthe regular disposition of the earth into like strata or layers of matter,commonly through vast tracts, and from whence I make a question, whe-ther fullers* earth may net be found in other parts of the same ridge ofsand hills, among other like matter.’*

We must observe however that the author has fallen into an error insupposing Newmarket heath, which in truth is occupied by the chalk for-mation, to be the continuation of this chain of hills.

Sections of the Ochre pits, Shotover hill.

feet inches

Beds of highly ferruginous grit, forming the summit

of the hill.6

Grey sand.3

Ferruginous concretions. ]

Yellow sand. 6

Cream-coloured loam. 4

Ochre.0 6

Beneath this is a second bed of ochre separated by a thin bed of clay;then succeeds an interval of nearly 40 feet occupied by various alternationsof ferruginous and sometimes cherty and argillaceous loams of a deepcream colour ; beneath these is the formation of Aylesbury limestone.

+ The soil of Penhurst is gravelly to an intermediate depth: at the bot-tom of the Earl of Ashburnham’s park, sandstone is found, solid enoughfor the purposes of masonry. Advancing up the hill, the sand rock is 21

s %