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 A HISTORY OF NORFOLK and porches in East Anglia. The Old Bridewell by St. Andrew's Church, in Norwich, is a fine example of flint-work dating back to about 1400. The faces of the flints often exhibit tiny conchoidal fractures, which were no doubt produced when the blocks of flint were fixed by the workmen ; subsequently the tiny portions of fractured flint have weathered out. Gun-flints have until comparatively recent days been manufactured at Catton and Whitlingham, near Norwich, and also at Broomhill on the Norfolk side of the Little Ouse, near Brandon.^ At Grime's Graves, in the parish of Weeting, in Norfolk, and about three miles north-east of Brandon, a number of ancient flint-pits occur, and these were sunk in prehistoric times through 10 or 15 feet of sand into the Chalk and to a particular layer of flint. In one working this layer was found to be 39 feet from the surface. It is the same bed as that from which gun-flints have more recently been made. In the ancient excavations, which were explored by Canon Greenwell, the flint-mining had been carried on mainly by means of picks formed from antlers of the red deer, many of which were discovered.* In these and other pits, as remarked by Sir John Evans, there appears to have been in very early days an organized manufactory for flint instruments.' Along the borders of the river Bure, as at Horstead and Wroxham, picturesque canals for wherries have been formed as the Chalk has been excavated in the hill-sides. As a water-bearing formation the Chalk in England stands foremost. In Norfolk it is largely covered with Drift deposits, and hence does not directly receive so much of the rainfall as it does in some other counties. This is more especially the case in the eastern portion of Norfolk ; nevertheless good supplies of water have been obtained by boring at Cromer, Mundesley and North Walsham, as well as at Norwich. On the western side of the county the Drifts are thinner, less continuous, and less impervious than on the east. The mass of the Chalk in Norfolk down to the Gault is practically porous, and the water falling on it would tend generally to move eastwards over the gently inclined floor of the Gault, until the whole being saturated the surplus above sea-level would escape in springs along the base of Chalk cliffs, in the deeper valleys, and along the western margin over the lip of Gault clay. Occasional marl seams and tabular masses of flint locally arrest supplies of water. The plane of saturation varies of course with the amount of rain, and this underground water-level falls to some extent with the slope of the ground, so that in West Norfolk it descends gradually westwards towards the outlet taken by the springs. As the saturation-level rises so springs break out at higher horizons, and instances of bournes are met with after much rain. Thus the Babingley stream, which ordinarily rises about half a mile above Flitcham Abbey, after heavy and prolonged rain rises (as observed by Mr. Whitaker) at ' Evans, Ancient Stone Implements, etc., of Great Britain, ed. 2, 1897, pp. 33-35- IC
 * S. B. J. Skertchly, ' Manufacture of Gun-flints' ifieol. Survey), 1879.
 * Greenwell, Journ. Ethnol. Soc, vol. ii., 1871, p. 425.