1746-1823

French physicist who formulated Charles law—at constant pressure, a gas's volume is inversely proportional to temperature (1787). Unaware of Guillaume Amontons' original, unpublished discovery (1699), Charles communicated his results to Joseph Gay-Lussac, whose superior experimental techniques yielded more accurate measurements. Published by Gay-Lussac (1802), the relationship is often referred to as Gay-Lussac's law. Charles contributed significantly to ballooning, developing and ascending in the first hydrogen balloon (1783) and inventing the valve line, appendix, and nacelle.