The Plateau Gravels, 8evenoaks. 405 



fine sand is interesting on account of its diverse nature, consisting 

 chiefly of angular fragments of quartz, with numerous subangular 

 and partially rounded quartz and flint grains, and very rarely 

 a probably wind-polished grain of quartz. A sponge-spicule was 

 noticed in this sample. 



E. — An umber-coloured clay, from Pit No. 2, at 8 feet. This 

 specimen yielded a residuum, on washing away the fine argillaceous 

 portion, of 42 per cent. This consists of fine angular quartz sand, 

 and a smaller proportion of accreted particles, of an umber-brown 

 colour. 



F. — A bright ochreous yellow sandy rock, of fine texture, from 

 Pit No. 2, at 8 feet. The fine argillaceous and ochreous portions of 

 this rock were separated by decanting after stirring and allowing 

 the washings to settle for 20 seconds. This gave a residuum of 

 72 per cent. The fine portion consists of minute grains of quartz, 

 very angular, and associated with them were some flakes of limonitic 

 material. A small proportion of the residue is much coarser and 

 floats easily. It consists of tubular and reticulose or pitted fragments 

 of a purple-brown colour, somewhat of the nature of ' race.' The 

 reticulate surface may possibly be due to the impress of sandtgrains. 

 Some of the particles in this residue have a chalky appearance, and 

 are doubtfully comparable with worn specimens of foraminifera ; 

 there are also a few fragmentary sponge-spicules. The rarer 

 minerals are also present in some abundance in this sand, such 

 as zircon, tourmaline, rutile, and kyanite. 



G. — A pale ochreous sandy clay, from Pit No. 2, at 8 ft. 2 in. 

 The residuum after washing was 40 per cent. The chief part of 

 the sand consists of angular and subangular quartz grains, with 

 a smaller quantity of flinty particles, and with a few larger accreted 

 fragments of a dark umber colour. Some of the large quartz grains 

 show evidence of wind-polishing. 



H. — Sand with iron-oxide cemented to an eolith, from a pit at 

 Ash in the gravel that occurs at 8 feet. The separated sand-grains 

 carry a more or less thick covering of ferruginous cement. The 

 finer sand-grains consist of sharply angular quartz fragments ; the 

 larger grains are angular, subangulai', and rounded, or even highly 

 polished, fragments of quartz, chert, and flint. Several of the 

 particles noticed are of foraminiferal origin, consisting of pale 

 glauconite. One very perfect cast, in apple-green glauconite, was 

 here noticed, and identified as that of Glohigerina cretacea, D'Orb. 



Belies of minute marine fossils (some certainly from the Chalk) 

 occur in the samples of loams and sands, D, F, and II. The sand- 

 grains of flint, chert, glauconite, and quartz are referable, of course, 

 to the Chalk, Greensands, and to some more ancient rocks, and may 

 have passed through several stages of erosion and sedimentation 

 before their deposition in these gravel-beds. The presence of the 

 rarer ' heavy tniuerals ' indicates very much older rocks as their real 

 source ; but they probably formed part of other beds in succession, 

 as, for instance, in the Bagshot Sands, to which allusion is made in 



