 By numerical powers I understand such powers as motions and figures of the same species. The power of the eye to contribute towards seeing is a species of motion, and the roundness of a body is a species of figure. By generical powers I understand all the several species of numerical powers—as motion signifies all the various species of motion, and figure all the various species of figure. (Clarke 1738 [1928: 805–806]; Clarke and Collins 2011: 124–125) 