THRESHING (from thresh, AS. perscan, paysenn, Goth. priskan, OHG. drescan, Ger. dreschen, to thresh; connected with Lith.
keti, to rattle, ()Church Slay. thrycshtiti, to strike) and THRESHINO MACHINES. Thresh ing is the separating of the grain o• seeds of plants from the straw or haulm, a process which has been accomplished in various ages and coun tries by sundry means more or less effective. The first method known to have been practiced was the heating out of the grain from the ears with a stick. An improvement on this method was the practice of the ancient Egyptians and Israelites of spreading out the loosened sheaves of grain on a circular piece of hard ground and driving oxen over it, so as to tread the grain out ; but as this mode was found to damage a portion of the grain, it was partially superseded in later times by the threshing-sledge, a heavy frame mounted on three rollers. which was dragged over the heaps of sheaves. The method of treading out the grain or seed, however, is still used to a limited extent on small farms in the United States, especially in case of buckwheat, (-lover, beans, etc. Similar methods of threshing were employed by the Greeks and Romans, the stick (fustis, bo(ulum, pertica), the treading by men or horses, and the threshing-sledge (tribulum) being found in com mon 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 modifica tion of it, the flail, is still used to a limited ex tent in Europe and America. The flail consists of two sticks loosely fastened together at one end by stout thongs; one stick is used as a handle by the workman, and by a circular swing around his head he brings down the other stick hori zontally on the heads of the loosened sheaves spread out on the barn-floor.
Early but unsuccessful inventions to supersede the flail by a machine, both in England and Amer ica, were largely of the rotary beater or flail type. In 1786, however. Andrew Meikle, an ingenious Scotch mechanic, produced a threshing machine so perfect that, despite nearly a century of im provers, it is essentially the machine of its in ventor. In Alcikle's machine the mode of opera tion is as follows: A sheaf is loosened and spread out on the feeding-board, with the ears toward the machine: it is then pushed forward till caught between two revolving fluted rollers of cast iron, a new sheaf taking its place as soon as the first has disappeared. 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 pro truded from between the rollers, detach the seeds and husks. Grain and straw then pass together over the cylinder, the grain falling through wire work, the straw being passed forward by circular rakes, which thoroughly toss and separate grain and chaff and then eject the straw. The grain
which has fallen through the wirework is re ceived into a winnowing machine, where the chaff is blown out, etc., and is then either discharged or, as in 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. Previous to the second winnowing, barley is subjected to the process of hummeling, by which the awns are removed.
INIodifications of Meikle's drum in which the two grooved cylinders were dispensed with were employed to some extent in threshing machines in England and America, hut have been almost entirely superseded in modern machines by a high-speed cylinder with radial teeth playing between inwardly projecting teeth set in a fixed concave or section of a cylinder. Prior to 1840 little progress was made in perfecting the thresh ing machine in America. Since that date im provement has been rapid, and the modern Ameri can machine with a capacity of 1000 bushels per day is a marvel of ingenuity and efficiency. In its most advanced form it cuts the bands of the sheaves and feeds itself; thoroughly separates the grain from the straw, winnows the grain and deposits it in sacks or loads it into wagons; re moves the straw and stacks it. The figure shows the interior construction of a modern thresher. The concave is open and has in rear au open grate so that the larger part of the grain is separated from the straw at this point and is conveyed di rectly to the fan. A considerable portion, how ever, still remains in the straw and can lie sepa rated only by further agitation, which is secured by the vibrating separator, revolving pickers or beaters, and shaking forks shown in the centre of the machine to the rear of the cylinder. These devices beat the straw thoroughly, at the same time conveying it to the rear of the machine, where it is taken by the stacker, which consists either of an elevator or tube with blast. The separated grain drops through the perforated bottom of the separator and with the grain com ing directly from the drum is carried to the fan ning mill by means of a vibrating platform or conveyor located immediately beneath the sepa rator. The parts of the modern thresher are in large measure adjustable. so that the machine may be adapted to different kinds of grain and to a variety of conditions, hut separate machines for special purposes are alto made, as, for in stance, for threshing rice, peas and beans, pea nuts, clover, and for husking maize and shredding the fodder. Inventive genius is also being large - ly exercised in de vising ingenious accessories to the thresher proper, such as automatic hand cutters and feeders, stackers, and grain meas urers and loaders. The motive power most commonly used for driving threshing machines is horse power or steam. The former was most common in the earlier days of the threshing machine, hut has been largely superseded by the portable steam-engine. Engines with straw-burn ing furnaces have been used in Hungary and in the rice regions of the United States.