Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/251



VI. Outlines of the Geology of Cambridgeshire.

By the Rev., F.R. & L S. Woodwardian Professor in the University of Cambridge.

Read November 18th, 1814.

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