THRESHING is the separating of the grain or seeds of plants from the straw or haulm, a process which has been accomplished in different ages and countries by means less or more effective. The first method known to have been practiced was the beating• out of the grain from the ears with a stick. An improvement on this method was the practice of the ancient Egyptians and Israelites to spread out the loosened sheaves of grain on a circular piece of hard ground 50 to 100 ft. in diameter, and to drive• oxen backward and forward over it, so as to tread the grain out; but as this mode was found to damage a portion of the grain, it was partially superseded in later times by the threshing-sledge (Egypt. noreg, cf. Heb. moreg), a heavy frame mounted on three• rollers, which was dragged over the heaps of sheaves. The use of the stick was, how ever, retained for threshing the lighter kinds of grain. Similar methods of threshing were employed by the Greeks and Romans, the stick (fustis, baculum, portico), the treading by men or horses, and the threshing-sledge (tribulum) being found in common use among them; but their threshing-sledge, which is still to be seen in operation in Greece, Asia Minor, Georgia, and Syria, differed from the eastern one by having pieces of iron or sharp flints fastened to the lower side, in place of rollers. The primitive implement in northern Europe was the stick, and an improved modification of it, the fail, has not yet been completely superseded. The flail consists of two sticks loosely fastened together at one end by stout thongs (caplins), one stick (the hand-staff) is used as a handle by the workman, and by a circular swing round his head he brings down the other stick (the staple) horizontally on the heads of the loosened sheaves spread out on the barn-floor. In the hands of a good workman this implement is found to perform its work pretty effectively, although slowly.
Various attempts were made to supersede the flail by a machine, but with little sue cess, till 1787, when Andrew 3leikle, an ingenious Scotch mechanic, produced a thresh ing-mill so perfect, that even after having run the gauntlet of nearly a century of improvers, it is essentially the machine of its original inventor. In Meikle's mill the mode of operation is as follows: The sheaves are loosened and spread out one by one on the feeding-board, with the ears toward the machine; they are then pushed forward tilt caught between two revolving fluted rollers of cast-iron; and as soon as one sheaf disap pears between the rollers, another is presented to them. Behind the rollers is a rapidly
revolving drum or cylinder, having four beaters or spars of wood armed with iron placed along its surface parallel to its axle; and these beaters striking the heads as they are protruded from between the rollers, detach the seeds and husks. Grain and straw then pass together over the cylinder, the former falling through wire-work, while the straw is carried forward by circular rakes, and, being by them thoroughly tossed and sepa rated from the grain and chaff, is then ejected. The grain which has fallen through the wireworkis received into a winnowing-machine, where it is cleansed from chaff, etc., and is then either discharged upon the barn-floor, or, as is the case with the most improved machines, is raised by a series of buckets fixed on an endless web, and again winnowed, to separate the perfect grains from the light and small seeds. Barley is, pre vious to the second winnowing, subjected to the process of " Immineling," by which the awns are removed; but the rest of the process is the same as above.
Since Meikle's invention, the improvements attempted on his milt have been chiefly confined to modifications of the drum; such as diminishing the distance between the drum and its cover; increasing the number of the beaters, and accelerating the speed of the drum.
The portable threshing-machine, now so generally employed in England and Scotland, has not the two grooved rollers, the loosened sheaf being at once submitted to the action of the threshing-machinery; the drum, which is a high-speed drum, is provided with six beaters, and its cover is capable of being set at any required distance from it by means of screws. A modification of thins machine has the drum wide enough to allow of the straw being fed in sideways; the cover incloses the machine for about three-fifths of its circumference; and the straw, after separation from the grain, is delivered by the rakes almost unbroken, and in a condition fit for being at once put up in bolts, or bundles, whence this species of drum is called abetting-drum. In another form, the drum is armed with rows of spikes projecting outward for about 2i in., which revolve between similar rows of spikes on the interior of the cover ; this kind threshes effectually, but breaks and chops the straw much more than the other forms of drum.