RECENT PROGRESS IN AERIAL NAVIGATION. 305 



Meanwhile the success achieved by the Tissandier brothers in 1881 

 and 1883 had inspired MM. Renard and Krebs, officers of the French 

 army, who were stationed at Chalais-Meudon, near Paris. They had 

 for several years been conducting experiments on the conditions requi- 

 site for directing balloons, being guided in their studies by the pre- 

 vious work of Dupuy de Lome. An appropriation of one hundred 

 thousand francs had been granted them, during Gambetta's brief ad- 

 ministration, and their investigations were conducted with the utmost 

 secrecy. The pecuniary resources at their command gave them a 

 great advantage over Tissandier, in the ability to construct a balloon 

 much larger than that with which Tissandier's success had been 

 achieved ; and this permitted the application of a motor nearly seven 

 times as powerful as the one previously employed. Their balloon 

 (Fig. 4) is one hundred and sixty-six feet long, twenty-eight feet in 

 greatest diameter, its capacity sixty-seven thousand cubic feet, and 

 ascensional power nearly five thousand pounds. The ratio of length 

 to thickness is thus much greater than in Tissandier's balloon. The 

 details of construction of the battery and motor have not been given 

 to the public by Captain Renard. The rudder is almost a parallelo- 

 gram in form, and thickest in the middle, the cloth being tightly 

 stretched over a light framework so as to present a rigid surface to 

 the air. The propeller is fixed to the extremity of a long shaft, and 

 placed at the front, instead of rear, of the balloon. The front end of 

 the machine is thicker than the rear end. This feature seems rather 

 unaccountable. The balloon is filled with hydrogen, but within it is 

 a subsidiary balloon, connected by a tube with the cage, where air 

 can be pumped in or out at pleasure, thus varying slightly the specific 

 gravity of the mass as a whole and enabling the aeronauts to vary 

 their elevation at will. 



On August 9, 1884, an ascent was accomplished with this balloon, 

 the atmosphere being almost perfectly calm. A journey of nearly 

 two miles was made in a southerly direction, then over a mile west- 

 ward, after which the balloon was turned northward and eastward. 

 Very slight motion of the rudder was needed to execute these curves. 

 Twenty-three minutes after their flight was begun the aeronauts were 

 immediately over their starting-point, having made a trip of not quite 

 five miles. In descending it was necessary to move backward and 

 forward several times in succession, alternately reversing the direction 

 of rotation of the propeller. The return to the ground was at the 

 very spot from which the departure had been made. This remarkable 

 feat was thus accomplished almost exactly one hundred and one years 

 after the ascent of the first hydrogen balloon, sent up by Charles 

 from a point but a few miles distant. 



A second ascent was made by Renard and Krebs on the 12th of 

 September, but with only partial success, in consequence of an acci- 

 dent to the motor. On the 8th of November two successive journeys 



VOL. XXVII. 20 



