. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. try round London is more or less covered by beds of drift, which protectthe outcropping beds of 6, and turn ofi a portion of the water falling upon them. The drift difiers considerably in its power of interference with tlie passage of the rain waterinto the strata beneath. The ochreous sandy flint gravel, forming so generally the subsoil ofLondon, admits of the passage of water. All the shallow surface springs, from 10 to 20 ft. deep,are produced by water which has fallen on, and passed through, this grave
. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. try round London is more or less covered by beds of drift, which protectthe outcropping beds of 6, and turn ofi a portion of the water falling upon them. The drift difiers considerably in its power of interference with tlie passage of the rain waterinto the strata beneath. The ochreous sandy flint gravel, forming so generally the subsoil ofLondon, admits of the passage of water. All the shallow surface springs, from 10 to 20 ft. deep,are produced by water which has fallen on, and passed through, this gravel, g^ Fig. 1503, down tothe top of the London clay, a, on the irregular surface of which it is held up. When the London clay is wanting, this gravel lies immediately upon the lower tertiary strata,as in the valley between Windsor and Maidenhead, and in that of the Kennet between Newbury andThatcham, transmitting to the underlying strata part of the surface water. Where beds of brickearth occur in the drift, as between West Drayton and Uxbridge, the -passage of the surface water Z-
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectenginee, bookyear1879
