Alice Rochester, age 10, of Grand Rapids, Mich., for her question:

WHO INVENTED THE GRAIN REAPER?

A reaping machine, used to harvest grain, actually started the mechanical revolution in agriculture. It was perfected and patented in 1834 by an American named Cyrus McCormick.

McCormick's machine was based on a number of different ideas that had been used by others for many years. He saw a great need for the reaper and came up with the right solutions.

At the time, the rich prairie wheatlands of the United States had two major problems: There were too few farmhands to do the harvesting and there was a tremendous amount of clear land just waiting for development.

McCormick's first reaper stood on two wheels. One was the main wheel, to which the gearing was attached. This wheel was of cast iron and had projections on its outer rim to keep it from slipping. The cutting part consisted of a horizontal steel plate called the cutter bar which was six feet long and about five inches wide.

The cutting on McCormick's first machine was done by triangular knives attached to a steel bar which slid forward and backward in a groove in the guards. The guards were long steel points which were riveted to the bar.

A crank operated by the gearing attached to the main wheel gave the knife bar a rapid motion. A divider separated the grain that was to be cut from that left standing. A reel bent the grain back against the knives and picked up the stalks that were bent, so that all the grain was cut.

As the grain was cut, it was laid on a platform. A man following the machine raked it off into piles.

At the age of 38 and with only $60, McCormick set up his own factory to manufacture reapers. Through years of court action and by purchasing other patent rights, he established his superiority and his machine became the leader. In 1902, his holdings were merged into the present International Harvester Company.

Before the reaping machine was perfected, a farmer had to use a hand sickle. It would take a whole day to cut the wheat on one acre of land. But the worst part was that before he could cut all of his crop, part of it would probably rot and not be worth harvesting.

Large wheat crops were impossible in the old days. Enough harvest time help was never available.

Today, in the United States and Canada, there are more than 700,000 reaping machines in operation. They are used to harvest oats, barley and rye as well as wheat.

The modern combine, as it is commonly called, is a combination harvester and thrasher. It cuts and thrashes the grain, all in one operation.