44. AERIAL NAVIGATION. 
teen men and attained a speed estimated at six miles an 
hour. Muscular power was thus shown to be far too 
uneconomical to be employed inthe direction of air 
ships. 
In 1881, Tissandier, a pupil of Giffard, keeping 
abreast with the progress of electrical science, conceived 
the idea of employing storage batteries as the immediate 
source of energy to actuate the propeller of an elongated 
balloon. He constructed first a small experimental 
balloon which he inflated with hydrogen. Upon a light 
platform beneath it was placed a single storage cell, a 
Siemens motor, and a propeller (fig. 2, page 43). This 
was exhibited at the Electrical Exposition of 1881, when 
FIGa3s 
a speed of about ten feet per second was attained. He 
then undertook the preparation of a much larger bal- 
oon on the same plan (fig. 3), in which he ascended on 
the eighth of October, 1888. The motor weighed one 
hundred twenty-one pounds, and was excited by a 
battery of twenty-four cells, in series, weighing three 
hundred fifty pounds. Its effective capacity for work 
