50$ Speculations of Dr. Black and Mr. Cavallo. [Book V. 



was filled with this air, as the mafs would be fpecifi- 

 cally lighter than the fame bulk of common air, it 

 would necefiarily rife in that fluid. A few years after- 

 wards Mr. Cavallo made fome experiments on this 

 fubjecl, and to him belongs the honour of bringing the 

 fuggeftion of Dr. Black firft into public notice, in a 

 paper which was read to the Royal Society on the 

 2Oth of June 1782. He found that the thinneft blad- 

 ders were too heavy, and that China paper was 

 permeable to the inflammable air j he proceeded there- 

 fore no further than blowing up foap-bubbles with in- 

 flammable air, which afcended rapidly to the ceiling of 

 a room, and broke againft it, and theie may be termed 

 the firft inflammable air balloons which were ever ex-, 

 hibited. 



While the art of aeroftation was thus on the point 

 of being difcovered in Britain, M. M. Stephen and 

 Jofeph Montgolfier, paper manufacturers at Annonay, 

 in France, diftinguifhed themfelves by exhibiting an 

 aeroftatic machine of confiderable magnitude *. 



After various inferior experiments, a grand one 

 was made at Annonay, on the 5th of June, 1783, 

 before a great multitude of fpectators. A flaccid bag 

 was fufpended on a pole thirty-five feet high ; draw 

 and chopped wool were burnt under the opening at 

 the bottom ; the vapour, or rather fmoke, foon inflated 

 the bag fo as to diftend it in all its parts, and this im- 

 menfe mafs afcended in the air with fuch rapidity, that 



* The principle upon which the aerial machines of MefTrs, 

 Montgolfier were conftrudled was that of air rarefied by heat, by 

 \vhich it became expanded, and therefore difpofed to afcend in the 

 common air. As in various other philofophical experiments, fo 

 in this of the two brothers, accident offered her precarious aid, and 

 they had the judgment to make a proper application of a cafual 

 difcovery. 



in 



