A device for plotting characteristic curves

A mechanical device for plotting characteristic curves of photographic emulsions is described. Details of construction are given, and readings from the instrument are compared with those obtained from an orthodox plot on graph paper. Considerable saving of time, and of material, may be effected by its use in instances where values of co-ordinates are to be entered from curves of similar character drawn through a series of experimental points, for which one set of co-ordinates has fixed values.