THRESHING. The separation of the grain from the ear in corn has always been one of the most laborious operations on a farm. Where the quantity grown is merely sufficient to supply food for the cultivators of the eoil, the simplest methods answer the purpose suffi ciently. The corn, taken by handfuls, may be beaten on a piece of wood or a table, and by repeatedly turning the straw the whole of the grain may bo readily beaten out. This mode of threshing may be still adopted in order to obtain the finest and ripest rains for seed ; but then the straw is afterwards threshed over again with the frail.
Where the corn is threshed out immediately after harvest, to be put into a granary, as is the ease in those countries where extensive tracts of rich land are sown with corn two or three times without much tillage or manuring, and then left to be recruited by several years' rest and pasture, the most common practice is to level a portion of a field, and, laying the corn in the straw in a large circle, to drive oxen and horses over it till it is all trodden out. This is the method alluded to In Scripture, and can only take place where the climate is serene and dry. Till Ingenuity had produced machines to supersede the flail, this was the only instrument in use. The first idea of a machine for threshing was that of imitating the motion of the flail ; but so much depends on the eye of the thresher, that no mechanism could well imitate the motion of his arms. The present improved threshing machine is now so common that it will suffice to give the general principle of action. A rapid motion is given to a hollow cylinder round a horizontal axis ; on the outer surface there are projecting ribs parallel to the axis at equal distances from each other; the width of these is from two to six inches. Around half the cylinder is a case,
the inner surface of which is lined with plates of cast-iron grooved in the direction of the axis. The ribs or beaters come quite close to these grooves, so that an ear of wheat or other corn cannot well pass between them without being flattened. The sheaves of corn, having been untied, are spread on a slanting table, and in some machines are drawn in between two iron rollers, of which one is plain and the other fluted. The motion of these rollers is slow, while that of the cylinder or drum is rapid. The beaters act on the straw as it comes through, and beat out most of the corny but what remains is carried in between the beaters and the fluted case, and when it has made half a revolution all the grain has been beaten and rubbed out. It falls on a shaker which lets the grain through, but tosses off the straw. Moveable threshing machines are very generally in use in England. The price of threshing in this way is about half of what is usually paid for threshing with the flail; it is more rapidly done, there is less chance of pilfering, and fewer grains remain in the straw.
On very large farms it has been found economical to erect a steam engine to work the threshing-machine, chaff-cutter, and other domestic implements. But travelling machines thresh out much the largest quantity of the corn that is grown in England. Tho moveable steam engines which are used for working such machines are now made in immense numbers, and no doubt 15,000 to 20,000 horse-power is thus every year added to the forces used in agriculture.