The "electric-phlogopneumatic" pistol was thought up by Volta. It was generally filled with a mixture of hydrogen and air, and then corked up. One of the electrodes was touched with one hand; the other hand touched one of the poles of an electrostatic machine. When the spark went off between them and also inside the pistol, a loud explosion resulted which violently shot out the cork As Volta himself wrote, these experiments "stupefied the ordinary observer… caused considerable satisfaction among amateurs and those in the know, for these are experiments combining electricity and inflammable air…" . They responded to the double requirement, which was popular at the time, of "being showy" and of popularising the latest scientific results.