In the fine section exposed in the cliffs between Herne Bay and the Reculvers, in England, a considerable mass of fossiliferous sands is seen to rise from beneath the London clay. Fig. 5 represents a view of a portion of this cliff a mile and a half east of Herne Bay and continued downwards, by estimation below the surface of the ground to the chalk. In this section there is evidently a very large proportion of sand, and consequently a large capacity for water. Again, at Upnor, near Rochester, the sands marked 3 are as much as 60 to 80 feet thick, and continue so to Gravesend, Purfleet, and Erith. In the first of these places they may be seen capping Windmill Hill; in the second, forming the hill, now removed, on which the lighthouse is built; and in the third, in the large ballast pits on the banks of the river Thames. The average thickness of these sands in this district may be about 50 to 60 feet. In their range from east to west, the beds 2 become more clayey and less permeable, and 1, very thin. As we approach London the thickness of 3 also diminishes. In the ballast pits at the west end of Woolwich, this sand-bed is not more than 35 feet thick, and as it passes under London becomes still thinner. [Illustration: Fig. 6. General Section of Strata below London.] Fig. 6 is a general or average section of the strata on which London stands. The increase in the proportion of the argillaceous strata, and the decrease of the beds of sand, in the Lower Tertiary strata is here very apparent, and from this point westward to Hungerford, clays decidedly predominate; while at the same time the series presents such rapid variations, even on the same level and at short distances, that no two sections are alike. On the southern boundary of the Tertiary district, from Croydon to Leatherhead, the sands 3 maintain a thickness of 20 to 40 feet, whilst the associated beds of clay are of inferior importance. We will take another section, Fig. 7, representing the usual features of the deposit in the northern part of the Tertiary district. It is from a cutting at a brickfield west of the small village of Hedgerley, 6 miles northward of Windsor. [Illustration: Unusual Deposit Features 6 miles North of Windsor. Fig. 7.] Here we see a large development of the mottled clays, and but little sand. A somewhat similar section is exhibited at Oak End, near Chalfont St. Giles. But to show how rapidly this series changes its character, the section of a pit only a third of a mile westward of the one at Hedgerley is given in Fig. 8. [Illustration: Section of a Pit. Fig. 8.]