Geographical Extent.—In a general sense, the cretaceous system ranges parallel to the oolitic formations from Yorkshire to Dorsetshire, and sends branches from the plains of Hampshire which border on the north and the south the Wealden formation of Kent and Sussex. The green sand formation is, in all parts of England, so closely connected with the chalk (except in Yorkshire, where it is almost deficient, and in Blackdown, Devon), that it appears unnecessary to notice more than the characteristic range of the chalk. This distinguishing feature of English geology overlooks the German Ocean at Flamborough Head, and sweeps in a large curve inland by Birdsall and Pocklington to the Humber, at Hessle; thence it pursues a south-eastward course to Candlesby in Lincolnshire; and, after the interruption of the "Wash," reappears in the cliffs at Hunstanton. Hence to StokeFerry its course is south; but it turns S.W., parallel to the oolities, by Cambridge, Baldock, Wendover, Wallingford, to above Wantage and Devizes. Hence it returns east to the sources of the Kennet, and gives origin to a great ridge (the North Downs) dipping north, and passing by Kingsclere, Guildford, Reigate, Wrotham, and Maidstone to Dover; which corresponds to another great ridge (the South Downs) dipping south, and passing from Beachy Head by Lewes, Steyning, Petersfield, and Alton, to join the North Downs at Farnham. From the sources of the Kennet to Salisbury, and from Farnham to Bishop Waltham, the chalk expands over a vast space in Hampshire; but its proper outcrop is the western boundary of Salisbury Plain, by Lavington,
