RECENT PROGRESS IN AERIAL NAVIGATION. 301 



way against this, and by the aid of the rudder to turn the machine into 

 any desired direction. He thus proved incontestably that the problem 

 of directing an aerial steamer was by no means insoluble. A second 

 ascent was accomplished by him in 1855, but under unfavorable con- 

 ditions. He made no further attempts with this machine, the aban- 

 donment of these experiments being due chiefly to their danger. A 

 steam-engine, sending forth sparks beneath a mass of thirty thousand 

 cubic feet of inflammable gas contained within an envelope of thin 

 cloth, is a source of peril to which few men would be willing to expose 

 themselves, even if lofty elevations were not reached. Trouble also 

 resulted from the fact that the weight of the balloon could not be kept 

 constant. The loss of the products of combustion and of spent steam 

 made it difficult to preserve the proper relation between the ascensive 

 power and the weight to be sustained. 



Not quite twenty years after Giffard's experiments the problem 

 was again attacked by M. Dupuy de Lome. His immense balloon, con- 

 taining one hundred and twenty thousand cubic feet of pure hydrogen, 

 was nearly similar in shape to that of Giffard. The car beneath was 

 capable of carrying easily fourteen men, seven of whom at a time were 

 employed in working a capstan which controlled the shaft of the pro- 

 peller, each of the two blades of this being about ten feet in length. 

 On February 2, 1872, Dupuy de Lome ascended in this balloon, and 

 attained a speed estimated at 2*8 metres per second, equivalent to 

 about six miles per hour. By means of the rudder he changed the 

 direction through an angle of 12. Giffard had attained an estimated 

 speed of four metres per second, or nine miles per hour. Muscular 

 power was thus shown to be far too uneconomical, while steam was 

 too dangerous, to be employed in the direction of aerostats. 



It was not until 1881, the year of Giffard's death, that electricity 

 was applied as a motive power in the attempt to solve the difficult 

 problem with which he had grappled. His pupil, M. Gaston Tissan- 

 dier,* had early imbibed a passion for aeronautics, and made many 

 successful ascents with spherical balloons. It was Tissandier who, in 

 company with two friends, ascended in April, 1875, to the height of 

 eight thousand six hundred metres, each of the three swooning on ac- 

 count of the rarefaction of the air, even before this limit was attained. 

 The same aeronaut, in company with Fonvielle, was borne by the wind, 

 in February, 1869, in thirty-five minutes, from Paris to Neuilly-Saint- 

 Front, a distance of fifty miles. Keeping abreast with the progress of 

 electrial science, Tissandier conceived the idea of employing storage- 

 batteries instead of steam or hand power, as the immediate source of 

 energy to actuate the propeller of an elongated balloon. He con- 

 structed a small experimental balloon, which was filled with hydrogen, 



* The writer talyes pleasure in acknowledging his personal indebtedness to M. Tissan- 

 dier for the full accounts from which the facts set forth in the latter part of this article 

 were obtained. 



