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THE POPULAR SCIENCE MONTHLY. 



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 



Jb'lO. 2. -TiSSANDLElt's MINIATURE ELECTRIC JilOTOK AND PROPELLER, 1881. 



"dirigeable" aerostat 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 con- 

 structing an aerostat large enough to lift two or three persons in addi- 

 tion to the weight of the propelling apparatus and other accessories. 



