On calculating the different weights of hot air, hydrogen gas, and common air, it has been found that a balloon filled with either of the two former will rise toward heaven till it is in equilibrium with the surrounding air, which may not happen until it has attained a great height.
The first experiment was made at Annonay, in Vivarais, MM. Montgolfier, the inventors; a globe formed of canvas and paper, 105 feet in circumference, filled with heated air, reached an uncalculated height.
The same experiment has just been renewed in Paris before a great crowd.
A globe of taffetas or light canvas covered by elastic gum and filled with inflammable air, has risen from the Champ de Mars, and been lost to view in the clouds, being borne in a north-westerly direction. One cannot foresee where it will descend.
It is proposed to repeat these experiments on a larger scale. Any one who shall see in the sky such a globe, which resembles 'la lune obscurcie,' should be aware that, far from being an alarming phenomenon, it is only a machine that cannot possibly cause any harm, and which will some day prove serviceable to the wants of society.
(Signed) DE SAUVIGNY.
LENOIR.