drift bolt

A rod used to drive out a bolt. drift-land, 8. Old Law: A yearly rent paid by some tenants for the privilege or right of driving cattle through a IMG:content-0529.png:[blocks in formation] Geol.: The period during which the drift described under DRIFT, II. 2. was deposited. Though there is no reason why it should not have recurred time after time during bygone geological ages, and perhaps it may be ultimately proved conclusively that it has done so, yet the term "drift-period" as a measure of duration is limited to the time commencing during the Newer Pliocene or Pleistocene, and terminating with the Post Pliocene or Post Pleistocene, during which drift was deposited in the latitudes in which we find it now. That it is e entially a glacial phenomenon is apparent from the fact that while becoming more marked in its character on this side the equator the further north one goes, it dies out about 50° N. latitude in Europe and 40 in North America. Hence it is often called Northern Drift. A corresponding development of it, however, exists in the Southern hemisphere. This becomes more marked as one approaches the Southern pole, and disappears between 40 and 50° S. latitude. Where it exists nearer the equator it is deposited around some giant mountain, the scratches and striations on the bowlders and pebbles radiating from the mountain on every side. The drift is now universally attributed, as Aga iz long ago suggested, to the action of ice, the only controversy remaining being whether land ice or floating icebergs took the chief part in its distribution. Hence it is often called, as by Sir Charles Lyell, Glacial Drift. In the Tabular view of the Fo iliferous Strata given in his Students ' Elements of Geology , "the Glacial drift of Northern Europe" is arranged as the oldest deposit of the Post Pliocene (q. v.). [GLACIAL PERIOD.] drift-piece, s. Ship build.: One of the upright or curved pieces of timber that connect the plank-sheer with the gun-wale.