motion, especially (but not necessarily) of an aimless sort, undirected
Thus it is possible to speak of a
See also:drift, an accumlation driven by the
See also:wind; of a
See also:ship drifting out of its course; of the drift of a speech, i.e. its general tendency . The word is also used in some technical senses, more immediately resulting from the
See also:action of
See also:driving something in . But the most important technical use of the word is in geology, as introduced by C .
See also:Lyell in 1840 in place of " Diluvium." The earlier geologists had been in the
See also:habit of dividing the
See also:Quaternary deposits into an older Diluvium and a younger
See also:Alluvium; the latter is still employed in England, but the former has dropped out of use, though it is still retained by some
See also:continental writers . The Alluvium was distinguished from Diluvium by the fact that its mammalian fossils were representatives of still living forms, but it is a
See also:matter of
See also:great difficulty to
See also:separate these two divisions in practice . " The
See also:term drift is now applied generally to the Quaternary deposits, which consist for the most
See also:part of
See also:gravel, sand,
See also:loam or brickearth and
See also:clay; it naturally refers to strata laid down at some distance from the rocks to whose destruction they are largely due; but, although applied to
See also:river deposits, the word drift is more appropriately used in reference to the accumulations of the Glacial
See also:period . " The occurrence of stones and boulders far removed from their
See also:parent source early attracted the
See also:attention of geologists, but for a long period the phenomena, now known as of glacial origin, were unexplained, and the drifts were looked upon as little more than ` extraneous rubbish,' the product of
See also:geological agents, quite distinct from those which helped to
See also:form the more solid ' rocks that underlie them." (See H . B . Woodward, The Geology of England and
See also:Wales, 2nd ed., 1887.) The conception of an -underlying " solid " geological structure covered by a superficial
See also:mantle of " drift " is still retained for certain
See also:practical purposes; thus, the Geological Survey of Great Britain issues many of the maps in two forms, the " Solid Edition," showing the " solid geology," which embraces all igneous rocks and the stratified rocks older than
See also:Pleistocene, and the "Drift Edition," which shows only such older strata as are unobscured by drift . In writing and in conversation the geological expression " drift " is now usually understood to mean Glacial drift, including
See also:boulder clay and all the varieties of sand, gravel and clay deposits formed by the agency of ice sheets, glaciers and icebergs . But in the " Drift " maps many other types of deposit are indicated, such, for instance, as the ordinary
See also:modern alluvium - of
See also:rivers, and the older river terraces (River-drift of various ages), including gravels, brickearth and loam; old raised
See also:sea beaches and blown-sand (Aeolian-drift); the "
See also:Head " of
See also:Cornwall and
See also:Devon, an angular detritus consisting of stones with clay or loam; clay-with-flints, rainwash (landwash), scree and
See also:talus; the " Warp," a marine and estuarine silt and clay of the
See also:Humber; and also beds of
See also:peat and diatomite .
See GLACIAL PERIOD; PLEISTOCENE; BOULDER CLAY . U . A .
DRIFFIELD (officially Great Driffield)
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