Hansen's writing ball, c 1880.
© Science Museum / Science & Society Picture Library
Many forms of typewriter were tried before practical machines emerged. The writing ball was invented in 1870 by Pastor Malling Hansen, the superintendent of a school for the deaf in Copenhagen, Denmark. Its spring-loaded type rods converge to a common point and are pushed down directly by the user, while the paper is moved by electrically-controlled clockwork to give the correct spacing of letters and lines. The impresion is made through a sheet of carbon paper, which obscures what is typed until the whole page is finished.