The British and American Patent Offices

1857 Scientific American  
� ticntifit �meritnn+ stringer of a flight of stairs, a spring is placed under the top of each, and on this lies the stair top, being divided and hinged on the sides, so that when a person ascends the stairs he has the fo rce of the spring to aid him in rising to the next, and in descending, the elasticity of the spring prevents the whole weight of the body from coming forcibly on the one foot, thus rendering" gitting up stairs" not snch a fatiguing affair as in the ordinary solid stairs .
doi:10.1038/scientificamerican09261857-22a fatcat:z62wwjup55hx7mw674iqdc2nea