HERO, the name of two celebrated Greek mathematicians; the one called the old, and the other the young, Hers. The younger was a disciple of Ctesibius. They are known by two works translated into Latin by Barochius: Spiralium liber, by Hero senior; and Tractat. artis et machin. militar. by Hero junior. They flourished about 130 and 100 B. C.