Hirn was the first to make a calculated value for the mechanical equivalent of heat for a man, an "animated motor", doing work in a sealed chamber, done probably similar to Antoine Lavoisier's combustion theory of animal heat experiments (c.1780) on humans.
To achieve this end, a man was placed in a hermetically closed chamber, and made to turn a wheel which could, at choice, revolve with or without doing work. The heat given out in the chamber was then ascertained by the ordinary calorimetric process. From these experiments, Hirn deduced a valuation of the mechanical equivalent of heat for animated motors; but the number which he obtained differed considerably from the standard obtained by James Joule through the standard physico-electric-mechanical methods. 
Education Hirn, owing to his delicate health, was never allowed to attend school, and instead was home-schooled in the large cotton mill of his maternal grandfather M. Haussman, where his father was also a partner. His first studies were in the chemical laboratory of the Mill. In 1845, at the age of thirty, he was placed in charge of the steam engines working the Mill, which is about what time he is said to have begun his serious work, an office he remained at for nearly thirty-five years.
Further reading ● Hirn, G. A. (1849). "New research on the friction of solid bodies," Comptes Rendus, 28, p. 290 ● Hirn, G. A. (1855). 'Studies on the main phenomena that are friction media and on the various ways of determining the value mechanics of the materials used in engine lubrication, "Bulletin de la Société Industrielle de Mulhouse, 26, p. 202 ● Hirn, G. A. (1855). "Notice on the laws of caloric output by friction media," Bulletin de la Société Industrielle de Mulhouse, 26, p. 238 ● Hirn, G. A. (1862). Mechanical Theory of Heat (Paris, Lieber) ● Hirn, G. A. (1863). Exhibition Analytical and Experimental Theory of Heat, (Paris, Mallet Bachelet). ● Hirn, G. A. (1887). "The thermodynamics and the work of living beings", Revue Scientifique, 22, May (Paris, Bureau journals), pp. 673-684.