118 ANNUAL KEPOR^ SMITHSONIAN INSTITUTION, 1908. 



surfaces, and are also often balanced so as to be slightly heavier than 

 the air in which they move, employing the propeller thrust and rudder 

 surfaces to control the altitude. 



I. Aerostation. 



Captive and free balloons, with the necessary apparatus and devices 

 for operating the same, have been for many years considered an essen- 

 tial part of the military establishment of every first-class power. 

 They played a conspicuous part in the siege of Paris, and were often 

 valuable in our own civil war. The construction and operation of 

 aerostats are too well understood to need further attention here. 



SUCCESSFUL MILITARY DIRIGIBLE BALLOONS. 



France. 



Two types of dirigible balloons have been used in the French army — 

 first, the Patrie, and, second, the Ville de Paris. 



The Patrie was developed by JuUiot, an engineer employed by the 

 Lebaudy Brothers at their sugar refinery in Paris. A history of his 

 work beginning in 1896 is fully given in La Conquete de I'Air. 



The Patrie. 



The Patrie, the third of its type, was first operated in 1906. The 

 gas bag of the first balloon was built by Surcouf at Billancourt, Paris. 

 The mechanical part was built at the Lebaudy sugar refinery. Since 

 then the gas bags have been built at the Lebaudy balloon shed at 

 Moisson, near Paris, under the direction of their aeronaut, Juchmes. 

 The gas bag of the Patrie was 197 feet long, with a maximum diameter 

 of 33 feet 9 inches, situated about two-fifths of the length from the 

 front ; volume, 111,250 cubic feet ; length, approximately six diameters. 

 This relation, together with the cigar shape, is in accordance with the 

 plans of Colonel Renard's dirigible, built and operated in France in 

 1884; the same general shape and proportions being found in the 

 Ville de Paris. 



The first Lebaudy was pointed at the rear, which is generally 

 admitted to be the proper shape for the least resistance, but to main- 

 tain stability it was found necessary to put a horizontal and vertical 

 plane there, so that it had to be made an ellipsoid of revolution to give 

 attachment for these planes. 



The ballonet for air had a capacity of 22,958 cubic feet, or about 

 one-fifth of the total volume. This is calculated to permit reaching 

 a height of about 1 mile and to be able to return to tlie earth, keep- 

 ing the gas bag always rigid. To descend from a height of 1 mile 

 gas would be released by the valve, then air pumped into the ballonet 

 to keep the gas bag rigid, these two operations being carried on alter- 



