THE MOTIVE POWER OF HEAT. 119 



recognition of this fact led Carnot, when but twenty-eight years old, 

 to undertake to lay the foundation on which all future progress was to 

 rest, by publishing in 1824 a small memoir, 'Reflexions sur la puissance 

 motrice du feu' ('Reflections on the Motive Power of Heat'). George 

 Stephenson made his wonderfully simple, but exceedingly effective, 

 improvements in the locomotive from 1814 to 1829, at a time when the 

 world was still ignorant of the value of Carnot 's ideas. To-day, how- 

 ever, when physicists fully realize the importance of his work, the 

 world at large is still ignorant of Carnot 's biography; and so it is 

 the purpose of this article to recall the life and character of him whose 

 name must always be intimately associated with the development of 

 tbe modern 'heat engine' and its influence upon civilization. 



Carnot 's father, Lazare Nicholas Marguerite Carnot, soldier and 

 statesman, was a member of one of the oldest and most distinguished 

 families in France. Educated as a military engineer, he gained a 

 second lieutenancy at eighteen and in later life won renown as a 

 mathematical writer. Minister of War under Napoleon, he took a 

 prominent part in the French Revolution and was regarded by his 

 countrymen as the genius and organizer of victory, exhibiting the 

 talents later illustrated by the German, Von Moltke. He voted against 

 the extension of the consulate and against the Empire, and was forced 

 into private life in the early days of the latter and died, proscribed, at 

 Magdeburg in 1823. Carnot 's brother, Lazare Hippokyte Carnot, was 

 twice a member of the Chamber of Deputies and also Minister of 

 Public Instruction. He died as recently as 1888. A fact which brings 

 Carnot 's life still closer to us of to-day is that the late president of 

 'France, Sadi Carnot, who was assassinated in 1890, was a grand- 

 nephew of the founder of thermodynamics, the subject of this sketch. 



Nicholas-Leonard-Sadi Carnot was born June 1, 1796, in the 

 smaller Luxembourg palace, a part of which was occupied by his father 

 as a member of the Directory. Christened 'Sadi' after the celebrated 

 Persian poet and moralist, he merited the name in that his nature 

 proved to be highly artistic as well as philosophic. Hardly a year after 

 Carnot 's birth, in consequence of his father's proscription and enforced 

 exile, his mother took refuge at her homestead in Saint Omer. The 

 boy's delicate constitution was so affected by the vicissitudes of his 

 mother's life that he regained his bodily powers later on only by 

 judicious exercise. He was of medium stature, gifted with extreme 

 sensibility and at the same time with extreme energy, generally 

 reserved, sometimes timid, but singularly quick upon occasion. When- 

 ever he believed that he was encountering injustice, nothing served to 

 restrain him. An incident, which his brother has described, exhibits 

 him in this light even as a child. 



