Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/737

1870.] gravel is considerable. Fragments of sarsen, or grey-wether sandstone, are met with everywhere, and blocks of considerable size are found in the gravel of the cliffs between Southampton Water and Gosport, and near Southampton, at 170 feet above the sea. A block of puddingstone, part of a larger mass, which is stated to have come from the gravel of Hordwell Cliff, is now in the Jermyn-Street Museum. Mr. Godwin-Austen has recorded the presence of waterworn specimens of white quartz, granite, and porphyry in the gravel on the high plain a little to the east of Poole, at about 160 feet above the sea; and white quartz-pebbles certainly occur as far east as Lymington. In the gravel covering Portsea Island, at a level not much above high water, numerous blocks of granite, syenite, and greenstone, as well as of sarsen-stone, are found. They are to be seen lying in the gravel-pits near Southsea, where the gravel is at least 27 feet thick, and covered with brick-earth, and in the excavation for the sewers they were frequently met with. They are rounded and smoothed boulders, from 1 to 2 cubic feet in size, and have undergone a partial decomposition, which renders them brittle. They do not appear to extend to the gravel on the west of Gosport, which is but little higher in level. They are probably derived from the same source as the similar boulders of Pagham and Bracklesham, namely, from rocks on the French side of the channel.

Brick-earth of a sandy nature is generally interstratified in the gravel in lenticular seams, and sometimes overlies it. The bedding is generally even and free from disturbance or contortion; and it is to be remarked that the contortions and foldings of the brick-earth and gravel usually attributed to glacial action are met with only at comparatively low levels. In the low gravel-cliffs to the south of Christchurch, near Brunage, and in a gravel-pit near Anglesea (Pl. XXXVII. fig. 14) the characteristic convolutions are seen; but the height at these places is not more than 30 feet above the sea. At heights ranging to 200 and 300 feet above the sea, the gravel is sometimes folded, apparently from the unequal wasting and subsidence of the clay or marl on which it lies. There is an instance of this near Chilworth "Tower of the Winds," at 300 feet above the sea, where the Bracklesham clay has so wasted and subsided (fig. 15). This action is more commonly observable at the edges of the plains, and in some cases from this cause the bedding of the gravel has been entirely effaced.

The general colour of the gravel is a deep red-brown; there is, however, a white gravel (so known locally and distinguished from the red or binding gravel) which is often met with and deserves some notice. It generally overlies the red gravel and penetrates it in potholes and pipes. It is loose and sandy, and the flints in it are white, with a curious porcelain-like lustre. The sandy matrix is sometimes dark with vegetable matter, and there is often a black carbonaceous band between the white gravel and the red (vide fig. 15). I believe that generally the white gravel has been formed in situ, and that its