Page:VCH Surrey 1.djvu/42

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A HISTORY OF SURREY are followed westward ; so that in Surrey there is some doubt as to their identification, and it is only in the tract between Reigate and Oxtead that the middle division, or Sandgate group, is recognized on the Geological Survey maps, though Mr. Meyer believes that it can be iden- tified also in the west of the county. 1 In Kent the lowest of these divisions, the Hythe Beds, is character- ized by irregular bands and concretions of sandy limestone or ' Kentish Rag,' often associated with layers of chert formed by the concentration of silica derived from sponge-spicules, but in eastern Surrey it consists, for the most part, of unconsolidated slightly loamy sand, with only occa- sional nodular induration. These characters are modified, however, west of Dorking, where the belt occupied by the Lower Greensand suddenly expands from a breadth of less than a mile to nearly four miles, again increasing to over six miles west of Guildford, under the influence of a subsidiary fold of the strata which will be subsequently described. Some parts of the division here become indurated into cherty sandstone ; and in the Guildford district a hard calcareous sandstone or grit known as 4 Bargate Stone,' resting on pebbly sands, is developed in the upper part, and this part contains, among other fossils, the teeth and scales of many extinct genera of fish. Sponge-spicules may generally be detected in the cherts, and the decay of such spicules appears to have supplied the siliceous cement by which the sands are indurated. 2 This lateral change in the composition of the beds is strongly reflected in the physical features of the country; for while between Reigate and Dorking, where the Lower Greensand includes very little hard material, its out- crop forms a comparatively low broken terrace dominated by the Chalk escarpment, it rises both eastward and westward into a bold hill-range which on the west is higher than the Chalk Downs, with its culminating points at Leith Hill (967 feet) and at Hind Head (894 feet) making the highest ground in the county. In the district east of Reigate, where the Sandgate Beds of the Lower Greensand have been recognized as a separate division, they consist of alternations of soft sandstone with clayey material and fuller's earth, having a total thickness near Nutfield of 40 feet or more. The fullers' earth of this district is of considerable economic importance, having been extensively worked from an early date for use in the preparing and cleansing of cloth, and latterly for export to America for use in the dehydrating of cottonseed-oil and other vegetable oils, which it is said can then be used for adulterating lard. The demand for the former purpose had gradually dwindled, but the new use for the material has given a fresh lease of life to the industry. The upper division, or Folkestone Beds, is persistent in character 1 'On the Lower Greensand of Godalming,' Proc. Geol. Assoc., sup. to vol. i., 1868 ; see also T. Leighton, 'The Lower Greensand above the Atherfield Clay of East Surrey,' Quart. Journ. Geol. Soc., vol. li. (1895) pp. 101-123, which contains full references to pre- vious literature of the subject.

  • See Dr. G. J. Hinde, Phil. Trans., vol. clxxvi. (1885) p. 403.