Charles, Jacques-Alexandre-C�sar 1746-1823
French experimental physicist

Born in Beaugency, Loiret department, he made himself an expert in popular scientific display. From 1781 he gave ingenious public lectures using an extensive collection of apparatus. Collaborating with the Robert brothers he made the first hydrogen balloon ascent in Paris in December 1783. He became a member of the Academy of Sciences (1795), and Professor of Experimental Physics at the Conservatoire des Arts et M�tiers. He invented a megascope, a hydrometer and a goniometer (for measuring angles of crystals). Unpublished experiments which he carried out between 1786 and 1787 showed that insoluble gas expansion followed the fundamental law which, in the UK, now bears his name. Joseph Gay-Lussac published the general law, extended to soluble gases, in 1802.