The long cliff of the London Clay extending along the northern side of Sheppey Isle furnishes abundance of Septaria, from which that excellent material for building under water and for stucco is made, and which is known by the name of Parker's Cement. Being separated from the clay by the action of the sea, they are collected on the beach, and exported to various places where they are calcined and ground. "In Hampstead and Highgate Hills in Middlesex, and in Boughton Hill in Kent, the layers of septaria occur about 50 feet below the summit. In Shooter's Hill they are very near the surface. At Epping, they were not found nearer than 100 feet beneath the grass, and continued to the depth of 300 feet.1 The London Clay forms a stiff tenacious soil, making good pasture-land, and yielding by the application of marl good crops of corn. Teazles are cultivated in Essex, and elm, oak, and ash timber in different places. The London Clay is impervious, and yields no water save in the basement beds. MIDDLE EOCENE. BAGSHOT BEDS. LOWER MARINE (old authors). The structure of the Bagshot Beds, so named from Bagshot Heath in Surrey, was first elucidated by Mr. Prestwich, who ascertained that they could be divided into three distinct and persistent divisions, severally characterized by peculiar groups of organic remains and by differences of lithological characters, thus: The series is perfectly conformable, and it is difficult to any hard lines between the divisions. draw Lower Bagshot Beds. This deposit consists of pale yellow or buff-coloured siliceous sand and loam, with seams of pipe-clay, and occasional beds of flint-pebbles. Ironstone veins and nodules are sometimes met with. The thickness varies from 100 to 150 feet. In the London Basin the beds locally show no inclination, but they are generally disposed with a slight dip to the southeast in the Isle of Wight they are highly inclined. (See fig. 20, p. 274.) Organic remains are exceedingly rare, only a few casts of mollusca having been found. The Leaf-beds (pipe-clay) of Alum Bay and Bournemouth have yielded many land-plants of sub-tropical genera, such as palms, maples, &c. Mr. Prestwich considers that the Lower Bagshot Beds were derived by denudation from the older crystalline and granitic rocks, but Mr. G. Maw has suggested that some of the fine white clays may have been due to the destruction of the Chalk. The pebble-beds in the Lower Bagshot series were first determined by Mr. S. V. Wood, jun. They occur at Brentwood, Stock, Billericay, and other localities in Essex. Their maximum thickness is 15 feet at Brentwood, where the section shows: From the Bagshot Beds themselves varying so much in section, and from the passage upwards of the London Clay into them, it is impossible to be certain as to the horizon taken as the junction of the two formations in the many outliers of Essex. Where a purely sandy condition prevailed at one spot a loam may have been formed at another, and a clay at a third. Again the test of level avails but little when it is remembered to what changes the area has been subjected in later times, during and after the Glacial Period: nor is it likely that the beds were spread over a uniform level; so that taking these points into consideration, it seems that the boundary between the Bagshot Beds and the London Clay must be drawn mainly with reference to the features of each outlier. Probably the best place for studying the Bagshot Beds in Essex is Brentwood, where the structure of both the sands and pebble-beds, and also their relation to the London Clay, are clearly shown. In the sections there the London Clay is seen to pass upwards into the Bagshot Sand. The brickyards well show the passage-beds, which consist of alternations of clays, sands, and loams, furnishing excellent brickearths. This passage makes the boundary-line between the two deposits very indefinite, and that line is liable to be taken at different horizons in different localities, even in the same outlier. There is no hard line anywhere, and it therefore becomes a matter of convenience, rather than of marked distinction, where to draw the boundary.1 Outliers occur at Langdon Hill, Rayleigh, High Beech, Highgate, Hampstead, and Harrow, forming some of the highest hills near London, and commanding extensive views: that from Langdon Hill in particular being surpassed by few in England. The beds are exposed in Alum and Whitecliff Bays in 1 Notes by II. B. W. in Mem. Geol. Surv. vol. iv. part 1. the Isle of Wight; at the former locality they attain a thickness of upwards of 660 feet. They are described by Mr. Bristow as a series of variously coloured unfossiliferous sands and clays, with seams of lignite and iron-sandstone. The clays are crowded with land-plants of sub-tropical genera. Mr. Bristow observes that the flora of Alum Bay (Alum Bay leaf-bed) is more especially distinguished by the number and variety of its Leguminosa, four species of which are known. The vegetation thus approximates to that of the London Clay. Fig-trees of lofty proportions, with long thick leaves, fig-sycamores with more delicate heart-shaped leaves, an Aralia with palmated leaves, must from their abundance have imparted a singularly majestic aspect to the vegetation of the period.1 Similar plant-remains have been found at Bournemouth, Studland, and Poole, but the distribution of the genera varies at each locality. The Poole Clay, so called from its being shipped at Poole, comprises beds of pipe and potter's-clay. It is worked between Wareham and Corfe, at Creech Grange, Nordon, and Rempstone; and is manufactured into ornamental tiles, tesselated pavements, &c. In the Isle of Wight this pipe-clay is almost entirely replaced by sands. Middle Bagshot Beds. In the Hampshire Basin these beds have been found to admit of two divisions: : 2. Barton Clay. 1. Bracklesham Beds. The whole series is, however, represented by the lower type (Bracklesham Beds) in the London Basin. Bracklesham Beds.-The Bracklesham Beds were so 1 The plant-remains have been described by Dr. De la Harpe. named from the remarkable series of strata displayed at Bracklesham Bay in Sussex. . They consist in Alum Bay, in the lower part, of clays and marls, overlaid by white, yellow, and crimson sands. The lower beds are remarkable for the lignite they contain, which is found in solid beds from fifteen inches to over two feet in thickness. Like true coal, each bed is based upon a stratum of clay, containing apparently the rootlets of plants. The deposit is a little more than 100 feet in thickness. In Whitecliff Bay the series is thicker, and the lower beds, consisting of green clayey sands, yield Cardita planicosta and Turritella imbricataria: the former species giving name to the Cardita bed. According to Mr. Bristow a hard bed of conglomerate, formed of rounded flint-pebbles, constitutes a strongly defined division between the Bracklesham Beds and Barton Clay. In Bracklesham Bay these deposits are often covered up with a few inches of sea-sand, and are only occasionally exposed to view. In Berkshire the Bracklesham Beds have a thickness of about 20 feet, and consist of alternations of grey clays, white pipe-clays, and white and yellow sands with pebbles. Barton Clay.-The Barton Clay, so well exposed in the cliffs of Barton and Hordwell in Hampshire, consists of grey and bluish-green clay and sands with septaria, altogether attaining a thickness of 300 feet. The Clays are very fossiliferous, and contain Rostellaria rimosa, Voluta luctatrix, Fusus longavus, Typhis pungens, Phorus, Calyptræa, Sanguinolaria compressa, Crassatella sulcata, Nummulites, &c. The Clay is used for making bricks. Upper Bagshot Beds. This division comprises white and pale-yellow, sometimes |