One year afterward, the inventor had seen Fourcroy, Prony, and the great scientists of his epoch. On the 28th of September, 1799, he took out a patent in which he gives a complete description of his thermo lamp, by means of which he produced a luminous gas, while at the same time manufacturing wood tar and pyroligneous or acetic acid. In this patent he mentions coal as proper to replace wood, and he explains his system with a visible emotion and singular ardor. In reading what he has written we are struck with that form of persuasion that does not permit of doubting that he foresaw the future in reserve for his system. Unfortunately, Lebon could not devote all his time to his discovery. Being a government engineer, without money and fortune, he had to attend to his duties. He went as an ordinary engineer to Angouleme, but he did not forget his illuminating gas, and he strongly regretted Paris, which he termed "an incomparable focus of study." He devoted himself to mathematics and science, he made himself beloved by all, and his mind wandered far from his daily occupation. The engineer in chief soon complained of him, but a committee appointed to investigate the charges that had been made against him affirmed that he was free from any reproach. He was sent back to his post, but war was decimating the resources of France, and the republic, while Bonaparte was in Italy, no longer had any time to pay its engineers. Lebon wrote some pressing letters to the minister, asking for the sums due on his work, but all of them remained without reply. His wife went to Paris, but her applications were fruitless. She wrote herself to the minister the following letter, which exists in the archives of the School of Bridges and Roads: "Liberty, equality, fraternity--Paris. 22 Messidor, year VII. of the French Republic, one and indivisible--the wife of Citizen Lebon to Citizen Minister of the Interior: "It is neither alms nor a favor that I ask of you, it is justice. I have for two months been languishing at 120 leagues from my household. Do not, by further delay, force the father of a family, for want of means, to leave a state for which he has sacrificed everything. ... Have regard for our position, citizen. It is oppressive, and my demand is just. There is more than one motive to persuade me that my application will not be fruitless with a minister who makes it a law and duty for himself to be just. "Greeting and esteem. Your devoted fellow-citizen, "Madame Lebon, _nee_ De Brambille."