VI. Outlines of the Geology of Cambridgeshire.
By the Rev. J. Hailstone, F.R. & L S. Woodwardian Professor in
the University of Cambridge.
The upland parts of Cambridgeshire consist of chalk hills,
being part of that great range which traverses the island in a south-easterly
direction, from Dorsetshire to the Yorkshire coast. At
their northern extremity they appear to rest upon an extensive
bed of blue clay, provincially called gault. They are composed
of both the varieties of chalk; of the upper containing the common
black flint in abundance; and the lower or grey chalk, which
contains little or none. If a line be drawn from Royston by
Balsham to Newmarket, it will pretty exactly define the limits of
both the varieties; the hills to the eastward being composed of the
upper beds, while those to the west consist of the lower or grey
chalk. Further to the east, on the borders of Suffolk and also of
Essex, the chalk disappears under a thick bed of clay, which
occasions a corresponding difference in the soil and its produce.
To the west, a succession of hills composed of beds of grey chalk
with wide intervening vallies of gault occur; till on the extremity
of the county, at Gamlingay and Potton, a tract of sand comes in,
evidently connecting the strata of Cambridgeshire with those of
Bedfordshire. And here the features of the former county undergo
