CAGNIARD DE LA TOUR

cagniard de la tour, charles (1777-1859), french engineer and physicist, was born in paris on the 31st of march 1777, and after attending the ecole polytechnique became one of the _ingenieurs geographiques_. he was made a baron in 1818, and died in paris on the 5th of july 1859. he was the author of numerous inventions, including the cagniardelle, a blowing machine, which consists essentially of an archimedean screw set obliquely in a tank of water in such a way that its lower end is completely and its upper end partially immersed, and operated by being rotated in the opposite direction to that required for raising water. in acoustics he invented, about 1819, the improved siren which is known by his name, using it for ascertaining the number of vibrations corresponding to a sound of any particular pitch, and he also made experiments on the mechanism of voice-production. in course of an investigation in 1822-1823 on the effects of heat and pressure on certain liquids he found that for each there was a certain temperature above which it refused to remain liquid but passed into the gaseous state, no matter what the amount of pressure to which it was subjected, and in the case of water he determined this critical temperature, with a remarkable approach to accuracy, to be 362°c. he also studied the nature of yeast and the influence of extreme cold upon its life.