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GEOLOGY gives indications of shallow-water conditions, for its sandy nature and the presence in it of lignite, as at Oakley north of Bedford, point to the proximity of land, while its ammonites indicate that a fairly deep sea was not far distant. The best sections are to be seen in the vicinity of Bedford, where it generally occurs as a calcareous sandstone with a thick bed of sand at its base and a thin layer of shelly limestone at its summit, from 7 to 10 feet of clay separating it from the underlying Cornbrash. The sandstone often takes the form of irregular concretions or ' doggers ' of varying size up to 10 feet in diameter imbedded in sand and some- times united in pairs like the figure 8. Many of these nodular concre- tions may be seen projecting from the sides of the cutting on the Midland Railway at Oakley. The clay contains selenite and ' race' ; the sand is destitute of fossils ; but the sandstone is very fossiliferous, having numerous Mollusca, including Myacites recurvus in abundance, and species of Ammonites, Ancy/oceras, P/euromya, etc. Grypbcea bilobata and Belem- nites oweni occur in shelly layers. Although the Oxford Clay is usually a greenish-grey and brown clay, it is by no means entirely clay. The following strata were pierced in a boring at Northill, three miles north-west of Biggleswade : — Boulder Clay, 104 feet. Oxford Clay : green clay, 12 ft. ; blue clay, 10 ft. ; blue clay and shells, 9 ft. ; dark green clay, 13 ft. 6 in. ; black stone, 4 ft. 6 in. ; greenish clay and shells, 20 ft. ; live sand, 9 ft. ; sandy blue clay, 9 ft. ; sand-rock, 7 ft. 4 in. ; blue clay and shells, 2 ft. 6 in. ; rock and blue clay, I ft. 9 in. ; limestone, 2 ft. 8 in. ; sandy blue clay, 3 ft. ; blue stone, 3 ft. 6 in. ; sandy clay, 4 ft. 10 in. ; limestone, 4 ft. ; sandy clay and stone, 3 ft. Total depth, 223 ft. 7 in. This section is of interest not only for the great variation which it shows in the strata which here constitute the higher portion of the Oxford Clay, but also in bringing to light such an enormous thickness of boulder clay. In giving it Mr. H. B. Woodward 1 says that ' portions of the upper beds grouped with the Oxford Clay may represent the Ampthill Clay.' Elsewhere there are bands of limestone near the top of the Oxford Clay, as at Sandy, 2 miles north-east of Northill, where there is stiff grey clay with ferruginous concretions, selenite, and a band of earthy limestone from 6 to 8 inches thick ; at Ampthill Park where the railway-cutting exposes dark blue clay with symmetrical crystals of selenite and seams of hard grey limestone varying from a foot to 18 inches in thickness ; and at Ridgmont and Aspley Guise near Woburn. The great mass of the formation, which attains a thickness of nearly 400 feet, is more homogeneous in character, indicating a prolonged period of deep-sea conditions over an extensive area, although near its base lignite and saurian bones have been found. It would appear that the sea-bed was sinking during its formation more rapidly than the sediment accumulated, and yet very slowly if the vast period of time which this accumulation must have occupied be considered. Its fossils are mostly pelagic forms, ammonites preponderating and Ammonites cordatus being 1 Jurassic Rocks of Britain, v. 51. 7