GEOLOGY According to Mr. Price, the most fossiliferous part is a sandy bed about 3 feet below the Upper Greensand. The sandy Upper Gault of Eastbourne is succeeded by loamy micaceous sands, which seem to pass laterally into the ' malmstone ' of west Sussex. This malmstone is a rock, of quite exceptional character ; it is defined by Mr. Jukes-Browne as a ' fine-grained siliceous rock, the silica of which is either principally of the colloid variety, either in the form of a semigranular ground mass or of scattered microscopic spheroids, or in both forms. Sponge spicules, or the spaces once occupied by them, are always abundant, and seem to have supplied the silica which is now in the globular semigranular condition. Quartz, mica and glau- conite are present, but generally in small quantities. There is always some calcareous matter, but in the purer varieties this does not amount to more than 2 or 3 per cent. Other varieties, however, contain as much as 20 or 25 per cent, and these are called calcareous mahistones ox fire- stones.^ Above the malmstone and loamy beds comes a mass of glauconitic sand or sandstone, calcareous in the upper part, and probably from 40 to 50 feet in thickness near Eastbourne. The total thickness of the Upper Greensand in western Sussex is estimated by P. J. Martin at about 90 to 100 feet,^ and this is probably the maximum in the county. The formation has not yet yielded many fossils, and it is still doubtful whether any part of it in Sussex represents the zone of Pecten asper ; the species found are not characteristic of particular zones. Up- wards the Greensand passes gradually into the Chalk, the sand becoming more calcareous and marly, till it gives place to the somewhat sandy marl which here forms the base of the true Chalk. Though, as already men- tioned, the Upper Greensand tends to form a ridge of sandy land, yet it is usually so dominated by the higher escarpment of the Chalk, that both the feature it makes and the character of the soil are masked and altered by material washed from the Chalk above. The Upper Greensand was probably woodland in prehistoric times. Chalk, as will be seen by the geological map, occupies the surface of nearly a third of Sussex, forming a sharply defined region of character unlike any other in the county, and known as the South Downs. It is the only limestone, with the exception of the few thin bands already mentioned ; and having a thickness of about 1,000 feet, hill and valley can be carved out of it without cutting into older rocks. Moreover, being without impervious beds except in the lowest 200 feet it forms a dry region, with no springs or flowing water except in the lowest valleys. The greater part of the Downs forms open rolling country, bare and treeless, but covered with excellent pasture, or with light, calcareous soil readily worked by the plough. These characteristics have always influenced the position of the settlements and the early history of the region ; for when ploughs and cutting tools were ruder and more clumsy, open pasture land with light and fairly good soil, not encumbered by trees, was far more valuable than the woodland which ' Geohffcal Memoir on a part of M'estem Sussex (410, London, 1828). I 9 2
