A cog is a tooth of a gear or cogwheel or the gear itself. After the closure of rack railway routes the cogwheel drive was removed. For multiple units, motor coaches and railcars with cogwheel drive there is an additional rule. A mercury-powered cogwheel clock was created by Ibn Khalaf al-Muradi. The method of Foucault replaces the cogwheel by a rotating mirror. The cogwheel refers to the long tradition of metalworking in the municipal area. A water-powered cogwheel clock was created in China by Yi Xing and Liang Lingzan. Magirus had shown the first cogwheel sliding ladder in 1864. Studs, cogwheel and heart-shaped ornaments of fainence and steatite were popular in Lothal. Following this, a cogwheel system was in use for about twenty years.