All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

240 All About Inventions But it was La France and the work of Renard and Krebs which really constituted the starting-point of aerial navigation. These two experimenters set out to build an airship fulfilling the following conditions: stability through the form of the balloon and arrange- ment of the rudder ; diminution of the resistance to its forward movement through selection of dimensions ; the approximate determination of the centres of traction and resistance in order to diminish the dis- turbing momentum of vertical stability ; and, above all, the acquisition of a speed capable of resisting the winds that prevail in France throughout three- quarters of the year. Each of the two experimenters assumed a definite responsibility in connection with the work. Renard devoted his mind to the study of the suspension covering, the determination of the capacity of the balloon—its gaseous content—the arrangements to secure longitudinal stability, the calculations for the dimensions of the details of the car and the invention and construction of a new type of accumulator possess- ing features of power and lightness. On the other hand, Krebs undertook the many details concerning the construction of the balloon and the means to unite it to the suspension covering, the building of the screw and rudder, the study of the electric motor which resulted in the construction of an engine of unprece- dented lightness, up to that time, for a given rating. The total weight of the airship, including ballast and the two aeronauts, was 4,391 pounds, of which the batteries represented 958 pounds. The electric motor, weighing 215 pounds, developed 8| horse- power at the propeller-shaft.