Page:Popular Science Monthly Volume 27.djvu/318

302 the effective ascensional force being two kilogrammes. A motor, of the Siemens type (Fig. 2), weighing only two hundred and twenty grammes, was made to turn the propeller, which consisted of a pair of vanes, each ten centimetres long; storage-cell, motor, and propeller being supported on a light platform suspended by netting. This



"dirigeable" aërostat was exhibited at the Electrical Exposition of 1881, and a bronze medal awarded to the inventor. It attained a speed of about three metres per second.

Encouraged by this success, Tissandier undertook the work of constructing an aërostat large enough to lift two or three persons in addition to the weight of the propelling apparatus and other accessories.