332 AERONAUTIC VOYAGES. 



with rain. The baHoon descended so lightly that it broke neither the branches 

 nor iVamcs of the vineyard ou which it finally rested." 



The gas employed in this experiment was nothing but air dilated by heat, 

 but its nature was not stated in the report of the ascension publit^hod in the 

 joui'uals. Without waiting for further indications, the artist Hobert and the 

 physicist Charles, by means of a national subscription, which was readily ad- 

 vanced, constructed, of lutestring coated with gum elastic, a balloon four meters 

 (13.12 feet) in diameter, which they filled with hydrogen gas, procured by 

 the action of diluted sulphuric acid on iron filings. This balloon ascended from 

 the Champ de Mars, August 27, 1783, at five o'clock in the afternoon, in 

 presence of an immense crowd, and heralded by salvos of cannon. It remained 

 but three-quarters of an hour in the air, and fell at Gonesse, near Econen, five 

 leagues distant from Paris. Thus was demonstrated the possibility of making 

 balloons of varnished material, nearly impermeable by hydrogen, the lightest 

 of known gases, and possessing great advantages over -the heated air. Yet this 

 means of obtaining very considerable ascensional force with balloons of limited 

 dimensions was not immediately adopted, and sundry experiments were suc- 

 cessively made with very large aerostats inflated with air heated by a fire of 

 straw mixed with a little wool. It was with such a balloon, having an oval 

 form, a height of 23 meters, a diameter of 15, and a capacity of 2,056 cubic 

 meters, that Pilatre do Roziers and d'Arlandes made the first aerial voyage 

 which man had ventured to undertake in balloons wholly detached and uncon- 

 fined. Ascending from the Chateau de la Muette, Nov^ember 21, 1783, they 

 traversed a distance of two leagues at an elevation of about 1,000 meters, having, 

 in their transit, hovered over Paris for 20 or 25 minutes. The 1st of December 

 following, Charles and Robert ascended from the Tuilleries in a spherical balloon, 

 made of lutestring coated with gum elastic, and having a diameter of only 8.50 

 meters, Avhich was inflated with hydrogen. After a passage of about nine 

 leagues the balloon touched the earth at Nesles, where Robert left the car, while 

 Charles reasceuded and reached an elevation of abcut 2,000 meters, alighting 

 finally two leagues further on, after having experienced a cold of — 5^, or -+- 

 23 Pah., when the thermometer indicated on the ground +7°, 44| Pah. Prom 

 this day dates the demonstration of the practical possibility of balloon voyages — 

 voyages always adventurous, but which have become, at a later period, a pastime 

 with per.-^ons of leisure. I shall not speak here of the attempts which have been 

 made to derive advantage from, aerostats in military expeditions, nor of the nu- 

 merous contrivances to direct their course throiigh the air, nor of the unfortunate 

 experiment of uniting the action of fire with the employment of hydrogen, for 

 which l*ilatre de Roziers atoned with his life, nor of the substitution of illumi- 

 nating gas for hydrogen, a substitution which renders these enterprises less 

 costly, but *rhich diminishes the ascensional force of apparatus of a determinate 

 dimension. I must restrict myself to aeronautic voyages, performed with a view 

 to the advancement of science. 



We must refer to the old Academy of Sciences if we would find*an account 

 of the first voyages by which science was benefited through the employment 

 of ballo >us, in which hydrogen gas was used as an agent. The expeditions of 

 MM. Biot and Gay Lussac, made in 1804, were preceded by the ascensions of 

 Robertson, Llioest, and Sacharoff, which yielded some interesting results ; but 

 not until after nearly half a century were the remarkable voyages of MM. Barral 

 aud Bixio undertaken, followed shortly afterwards by those of Mr. John Welsh. 



IF. — RESEARCHES TO BE MADE IN AEROSTATIC ASCENSIONS. 



Those who propose to undertake aerial voyages form, in general, no idea of 

 the number of questions to be resolved, nor of the difiiculties to be surmounted 

 in order to furnish science with certain elements of discussion. The instru- 

 ments requisite for investigating, as well the temperature as the hydrometric 



