How It Works: Seed separation with Eli Whitney’s cotton gin
Born in 1765 in Westborough, Mass., Eli Whitney began work as a blacksmith at a young age. Using a machine he built himself, he also was a nail maker and, at one time, was the country’s sole maker of ladies’ hatpins. After attending Yale College, he headed to South Carolina to work as a tutor. When he arrived, he learned his salary would be half what he was promised. Through a chance meeting, he ended up working at a plantation managed by Phineas Miller, who eventually became his partner in the cotton gin. Painting by Samuel F.B. Morse, 1822.
Woman working a cotton gin in an undated photo.
A cotton gin in use, from an 1869 engraving by William L. Sheppard.
Cut-away model of an early cotton gin at the Eli Whitney Museum and Workshop illustrates how cotton is separated from the seed. As cotton feeds from a hopper, saw-like teeth on a rotating cylinder grab the cotton fibers and pull them through a grate that holds back the seeds. A rotating brush then combs the cotton from the teeth and deposits it in a receptacle.
This 1880 cotton gin (on display at Pioneer Village Museum, Minden, Neb.) was built by Smith & Sons Gin and Machine Co., Birmingham, Ala. Hand-picked cotton bolls were dumped into the top hopper. Note the belt pulley, which allowed the machine to be mechanically powered.
Although Eli Whitney received a patent for his cotton gin on March 14, 1794, it was not validated until 1807. In addition, the sawtooth gin blades, illustrated here, were not part of Whitney’s original patent.
This early drawing shows how the cotton gin relies on three major components: a separating drum that pulls cotton from the seeds, a grid to hold back the seeds (in hinged cover) and a brush to remove fiber from the teeth.