Charles Cagniard de la Tour, French physicist and engineer (b. 1777)
Baron Charles Cagniard de la Tour (31 March 1777 – 5 July 1859) was a French engineer and physicist. Charles Cagniard was born in Paris, and after attending the École Polytechnique became one of the ingénieurs géographiques. He examined the mechanism of voice-production, invented a blowing machine and contributed to acoustics by inventing an improved siren. He also studied yeast.

In 1822, he discovered the critical point of a substance in his gun barrel experiments. Listening to discontinuities in the sound of a rolling flint ball in a sealed gun barrel filled with fluids at various temperatures, he observed the critical temperature. Above this temperature, the densities of the liquid and gas phases become equal and the distinction between them disappears, resulting in a single supercritical fluid phase.He was made a baron in 1818, and died in Paris. Despite several claims to the contrary, no portraits of Baron Cagniard de la Tour exist.