The combined header and thresher is most likely the most complicated and at the same time the most advanced type of harvester. It heads, threshes, cleans, and sacks the grain at one operation. It is used extensively in certain parts of the western United States and Aus tralia. Such machines are usually pushed through the grain either by a traction engine or by horses, a large number of the latter being necessary for each machine, the capacity of which ranges from 60 to 125 acres per day.
Mowing machines have kept step with the development of reaping machines, and, indeed, many mowers are designed so as to be used as reapers also.
Threshing machines are implements used to separate the grain or seed of plants from the straw or haulm. Not until the end of the eighteenth century did various attempts to supersede the primitive flail by mechanical imple ments succeed. In 1786 a Scotch me chanic, Andrew Meikle, designed a threshing machine which, in spite of the fact that many inventors have tried to improve it, remains today essentially the same. Practically all modern threshing machines are based on the principles first developed by Meikle. In America great ly improved threshing machines are now in use, most of the improvements having been made since 1840. The most up-to date threshing machine performs me chanically practically all operations in volving the cutting of the bands of the sheaves, automatic feeding, thorough separation of grain from straw, winnow ing and weighing the grain, depositing it in sacks or loading it into wagons, and removing and stacking the straw. Although there are in existence special threshing machines adapted to different kinds of grain and to a large variety of conditions, the parts of the most modern thresher are so adjustible that one and the same machine can be used for all kinds of grain and under all kinds of conditions.
Amongst the more important special threshing machines should be mentioned those for threshing beans, clover, pea nuts, peas and rice, and others for husk ing maize, and shredding fodder. As a rule, bean and pea threshers are equipped with two cylinders which run at different rates of speed. Still another additional cylinder for hulling is usually to be found in clover hullers. Many important
and useful accessory devices have been invented which are used in connection with threshing machines. The most im portant of these are automatic band cut ters and feeders, loaders, stackers, and grain measurers. In the early days of the threshing machine, horse power was used most frequently and it is still used to a considerable extent. However, port able steam engines and internal combus tion engines are gradually superseding horse power. In those parts of the United States where rice is cultivated engines with straw-burning furnaces have been used and have given satisfac tion.
Nowhere else has more progress been made in the use of farming machinery than in the United States, and the re markable productivity and prosperity which agriculture enjoys in this country are to no slight degree due to this fact.
The last United States census of the manufacturers (1914) shows 601 estab lishments devoted to the manufacture of agricultural implements of all kinds. These employed 58,118 persons; had a capital of $338,531,673; paid salaries and wages amounting to $47,603,790; and produced goods valued at $164,068,835. The export of agricultural implements from this country to foreign countries is of importance and is steadily growing. In 1890 the value of agricultural imple ments from the United States was $3, 859,184. By 1900 it had increased to $16,099,149. It then remained stationary for the next two years, increasing slowly until 1905, when it amounted to $20,721, 741. In 1910 it had reached $28,124,033. In the last year previous to the World War (1913) it reached the large sum of $40,572,352. The effect of the World War was especially noticeable in the agricultural implement industry. In 1914 the exports had fallen to about $32,000,000, and in 1915 to $10,300,000, a figure lower than any since 1898. A slight improvement was shown in 1916, with total exports of over $17,600,000; these rose, in 1917, to over $26,500,000; in 1918 to over $35,000,000; and in 1919 to $41,195,494, the highest total yet achieved. This, however, was exceeded in 1920, when the exports of agricultural implements were valued at $46,277,269.