Encyclopedia article on the cotton-gin from Appletons' Cyclopaedia of Applied Mechanics. It describes the ancient roller-gin and Eli Whitney's 1793 saw-gin, with a parts-by-parts account of an improved saw-gin (grate-fall, seed-board, saw-cylinder, brush, mote-board, patent detached grate). It also covers later designs, namely the Macarthy, Cowper lock-jaw, knife-roller and Scattergood needle gins, plus a self-feeding apparatus, and ends with a table of claimed capacities in pounds of cotton cleaned per hour.