(glass bulbs floating in a vessel of water), that puzzled many philosophers; in 1649 he sent one of these to Athanasius Kircher and one to Raphael Magiotti at Rome, with a challenge to explain the paradox, and both the Roman scientists published correct solutions. These instruments, of both the closed and the open forms, found many imitators, Guericke, Kircher, Dalencé, and Pasumot, but are not sufficiently accurate for thermometrical purposes.
In 1657 Ferdinand II, of Tuscany, and his brother, Prince Leopold de Medici, made a most valuable contribution to physical science in promoting the establishment in Florence of a society destined to become famous. The Accademia del Cimento, as its name indicates, was founded for the express purpose of ascertaining by experiment the facts and laws of nature; it numbered only nine members, most of them pupils of Galileo (who had died in 1642), besides a few foreign correspondents, and they devoted themselves to experimental research for truth's sake, taking as their motto "Provando e Riprovando." They did not even seek personal renown, for the results of their investigations were published in the name of the academy only, no individual being men-
