Lid and discs used by James Joule in friction experiments on solids, c. 1850. Circular lid with three arms on one side through which rods securing perforated discs are slotted. One disc is moveable by a rod; the lower disc is fixed. Used in a paddlewheel experiment to test the change in temperature brought about by the friction of solid bodies. Probably exhibited at Royal Jubilee Exhibition, Manchester, 1887 Lid and discs used by James Joule in friction experiments on solids
