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 A HISTORY OF SUFFOLK the surface it is usually decalcified, but where protected by Boulder Clay the Chalk and other calcareous fragments may be preserved. Sometimes, as near Lowestoft, this newer gravel extends irregularly from higher to lower ground, from Boulder Clay on to the Middle Glacial gravels, and where one gravel rests on another it is often difficult to determine any plane of separation. Occasionally a large erratic block has been met with, and J. E. Taylor obtained a mass of ' Hertfordshire puddingstone,' weighing about a ton and a half, from the sands near Ipswich. The Glacial sands and gravels have furnished local supplies of water to many a village and small town. The gravels are employed for road mending, and the larger flints are sometimes used for building purposes. Speaking generally, the sands and gravels form the less fertile areas in Suffolk, the so-called ' waste ' grounds which form the picturesque commons of East Suffolk at Walberswick, Dunwich and Westleton ; and the ' Sandlings ' which extend southwards from Saxmundham, Orford and Woodbridge. The neighbourhood of Yoxford has sometimes been termed the ' Garden of Suffolk.' Over much of the region mentioned, the Glacial sands and gravels rest on the porous shelly sands of the Crag Series, which are more fertile in character ; together they con- stitute the lighter lands of Suffolk. BOULDER CLAY The Chalky Boulder Clay occupies the surface over the greater part of central and western Suffolk, and it occurs in tracts along the eastern borders. In the central and eastern parts of the county it presents its characteristic features of a tough, bluish-grey, unstratified stony clay, with many small pebbles of Chalk, flints, and stones and fossils from a variety of geological formations, notably from the Secondary strata. Thus Red Chalk, Spilsby Sandstone, Kimeridge Shale and Oxford Clay, Oolites and Lias are represented, and we find Saurian bones, Ammonites, Belemnites, Gryph^a and other fossils. Much of the Chalk and many other blocks of rock, and sometimes fossils such as Belemnites, are scored and scratched, no doubt by sharp fragments, such as shattered flint, that were embedded in the ice to which the Boulder Clay owes its origin. It attains a thickness of from 130 to 150 feet at Wickhambrook, Naughton, Great Thurlow and Hartest, and 170 feet at Bradfield St. George. Elsewhere, as at Botesdale, St. Margarets Southelmham, Men- dlesham, Cockfield, Lavenham and southwards to Assington and Leaden- heath, it is from 50 to 100 feet. In western Suffolk, especially about Elvedon and on Icklingham Heath, the Boulder Clay is thinner, more chalky and more sandy, and often riot more than i 2 feet thick. Much of the Boulder Clay is obscured by a thin sandy soil, which Mr. F. J. Bennett regards as to some extent a decomposition product, and as feed- ing the sandstorms which arise.* 22
 * 'Geology of Diss, Eye, Botesdale and Ixworth,' Geol. Survey (1884).