ad many competitors, and some of them were in the field with
improved devices ahead of him, but he always held his own, either by
buying up the patent for a real improvement, or else by requiring his
staff to invent something to do the same work. Numerous new devices
to improve the harvester were patented, but the most important was an
automatic attachment to bind the sheaves with wire. This was patented in
1872, and McCormick soon made it his own. The harvester seemed complete.
One man drove the team, and the machine cut the grain, bound it in
sheaves, and deposited them upon the ground.

Presently, however, complaints were heard of the wire tie. When the
wheat was threshed, bits of wire got into the straw, and were swallowed
by the cattle; or else the bits of metal got among the wheat itself and
gave out sparks in grinding, setting some mills on fire. Two inventors,
almost simultaneously, produced the remedy. Marquis L. Gorham, working
for McCormick, and John F. Appleby, whose invention was purchased by
William Deering, one of McCormick's chief competitors, invented binders
which used twine. By 1880 the self-binding harvester was complete. No
distinctive improvement has been made since, except to add strength and
simplification. The machine now needed the services of only two men, one
to drive and the other to shock the bundles, and could reap twenty acres
or more a day, tie the grain into bundles of uniform size, and dump them
in piles of five ready to be shocked.

Grain must be separated from the straw and chaff. The Biblical threshing
floor, on which oxen or horses trampled out the grain, was still common
in Washington's time, though it had been largely succeeded by the
flail. In Great Britain several threshing machines were devised in the
eighteenth century, but none was particularly successful. They were
stationary, and it was necessary to bring the sheaves to them. The
seventh patent issued by the United States, to Samuel Mulliken of
Philadelphia, was for a threshing machine. The portable horse-power
treadmill, invented in 1830 by Hiram A. and John A. Pitts of Winthrop,
Maine, was presently coupled with a thresher, or "separator," and this
outfit, with its men and horses, moving from farm to farm, soon became
an autumn feature of every neighborhood. The treadmill was later on
succeeded--by the traction engine, and the apparatus now in common use
is an engine which draws the greatly improved threshing machine fro