Mike Steen, age 10, of Greenville, Miss., for his question:

HOW DOES THE COTTON GIN WORK?

A cotton gin is a machine used for separating cotton fiber from the seed. The machine, invented in 1793 by Eli Whitney, helped make cotton the chief crop of the southern United States.

Modern gins use the same principle as Whitney's first machine. Harvested cotton is fed through a row of about 70 saws that make from 350 to 500 revolutions a minute. The saws have a 12 inch diameter and are placed about five eights of an inch apart.

The teeth of the saws pull the cotton from the seeds. Ginning ribs between the saws prevent the seeds from passing through.

Brushes or air jets in the cotton gin remove the fiber from the teeth of the saw.

Before Whitney invented the gin, it took a person many hours to hand pick the seeds from a pound of cotton fiber. The machine made it possible to do the job in minutes.

The word "gin" comes from the old French "engin," meaning "engine."

Hand harvested cotton comes to the gin relatively clean. But machine picked cotton contains much more leaf stem trash. The modern gin must use additional equipment to clean the fiber.

A precleaner extractor removes much of the trash from cotton before ginning. It consists of a vertical column with four rows of saws, one above the other. As the saws rotate, they drag the cotton over grid bars that scrub off the trash. Brushes remove the cotton from the saws.

Whitney was born in 1765 in Westborough, Mass. He showed exceptional mechanical aptitude as a boy. He made a violin when he was only 12 years old, and he also made handwrought nails while he was in his teens during the Revolutionary War.

Later, while living in Georgia, Whitney came up with the cotton gin idea after seeing that there was definitely a need for such a machine.

However, Whitney ran into trouble with his invention, starting with a year lost in the red tape he met with his efforts in obtaining a patent.

Then Whitney had trouble when he found he couldn't make gins fast enough to meet the demand. More bad luck came when his factory burned down.

Soon others were making and using imitations of his machine. Whitney sued them. After long years of court trials, he finally won. The courts agreed that he had sole rights to his patent. But the life of the patent had almost run out. He asked for a renewal, but Congress refused to grant it.

In 1798, Whitney built another factory, this one to make muskets by a new method. Until then, each gun had been handmade by a skilled craftsman and no two guns were alike. Whitney invented tools arid machines so that unskilled workmen could turn out absolutely uniform parts.

Setting up the machinery took time. The government grew impatient and asked for the guns. Whitney amazed the government representatives by assembling guns from pieces chosen at random from piles of parts. Eventually, his arms factory made him rich.

Whitney was the father of mass production although this important fact about him is almost unknown today.