The French geologist and traveller Barthelemy Faujas de Saint-Fond (1741 1819) was a strong supporter of the aerostatic experiments of the Montgolfier brothers, seeking to publicise their pioneering endeavours in this 1783 work. Exploiting the principle that hot air is lighter than cold, the Montgolfiers developed and demonstrated their hot air balloons to great acclaim. In this collection of reports, Faujas presents the details of each experiment, describing the balloons as well as potential improvements. Where possible, he specifies the position of witnesses, precise timings and viewing angles. A number of finely engraved plates enhance the work, giving readers a flavour of the spectacle that impressed contemporary observers. Faujas published a second volume, containing additional accounts and illustrations, in 1784. His Mineralogie des volcans (1784) and Essai de geologie (1803 9) are also reissued in this series."