Revolution Counter, with five discs

Revolution Counter developed by engineer Richard Roberts, 1858.

This instrument, invented by Richard Roberts, consists of five wheels, each marked with the ten numerals on the edge; all but the first wheel run loose on the horizontal shaft of the counter. On one side of each wheel is a ten- pointed recess, and on the opposite side of the wheel is an eccentric boss; on each boss is a loose ring from which projects downward a tail that prevents its rotation, while from the face of the ring project three teeth, which engage in the recesses in the adjacent wheel. The result of this connection is that each wheel is driven at one-tenth of the speed of the wheel driving it, so that read along a horizontal line the revolutions are indicated in a very convenient form for reading; the advance of each wheel is, however, continuous, so that the trouble of half figures is not avoided.