Caption:
Jacques Charles and Nicolas-Louis Robert stepping out of their hydrogen balloon on a plain near Nesle, France after the first manned balloon flight in December of 1783. Jacques Alexandre César Charles (November 12, 1746 - April 7, 1823) was a French inventor, scientist, mathematician, and balloonist. Charles conceived the idea that hydrogen would be a suitable lifting agent for balloons having studied the work of Robert Boyle's Boyle's Law which was published 100 years earlier in 1662. Charles and the Robert brothers launched the world's first (unmanned) hydrogen-filled balloon in August 1783. On December 1, 1783, he and his co-pilot Nicolas-Louis Robert ascended to a height of about 1,800 feet in a manned balloon. The Robert Brothers (Les Frères Robert) were Anne-Jean Robert (1758-1820) and Nicolas-Louis Robert (1760-1820) skilled engineers with a workshop at the Place des Victoires in Paris.