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 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.
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.