The Directory giving place to the Consulate, Carnot senior, after two years of exile, reentered France, being called to the Ministry of War by Bonaparte, who, remembering Carnot 's services to him at the beginning of his career, wished to continue the intimate relations that had existed between them during the Directory. Often when the minister came to work with the consul he brought his son, now about four years of age, and left him in the charge of Madame Bonaparte, who was very fond of him. On one such occasion, Madame Bonaparte and some of her ladies, mounted on a little raft, were paddling about 
Lazare Nicholas Marguerite Carnot,
Father of Nicholas Leonard Sadi Carnot. upon a pond in the palace court. Napoleon, happening along, began to amuse himself by throwing stones at the raft so as to splash the water over the clean dresses of the would-be sailors. The latter feared to manifest their displeasure, but the little boy, after watching the procedure for a while, suddenly faced the conqueror of Marengo and, shaking a stick at him, cried: 'Animal of a First Consul, are you not ashamed to torment these ladies!' Sadi showed such interest in machinery and applications of physics that his father early directed his studies toward science, and he was just sixteen when he entered the Ecole Polytechnique in 1812. He made rapid progress, graduating the next year with first rank in the artillery. But he was thought too young for the military school at Metz, and was allowed to continue his studies at Paris for another year. Having fought with his gallant fellow-students at Vincennes in March, 1814, he returned when peace was established to his studies at the Polytechnique, but left in October with the rank of sixth-cadet of engineers and repaired to Metz as a sublieutenant in the school of practical fortifications.
The events of 1815 brought Carnot senior again upon the political field during the 'Hundred Days.' This was the occasion for Sadi to make a test of men, of which he never spoke afterwards without disgust. His little quarters of sublieutenant were visited by certain superior officers, who did not hesitate to mount three flights of stairs in order to greet the son of the new minister. Waterloo put an end to
