Dr. Franklin was subject to visits and calls from all descriptions of persons, making applications and inquiries without number. The following is the journal of a day.
Passy, December 13th, 1778. "A man came to tell me he had invented a machine, which would go of itself, without the help of a spring, weight, air, water, or any of the elements, or the labor of man or beast, and with force sufficient to work four machines for cutting tobacco; that he had experienced it; would show it me if I would come to his house, and would sell the secret of it for two hundred louis. I doubted it but promised to go to him in order to see it.
"A Monsieur Coder came with a proposition in writing, to levy six hundred men, to be employed in landing on the coast of England and Scotland, to turn and ransom towns and villages, in order to put a stop to the English proceedings in that way in America. I thanked him, and told him I could not approve it, nor had I any money at command for such purposes; moreover, that it would not be permitted by the government here.
"A man came with a request that I would patronize, and recommend to government, an invention he had, whereby a hussar might so conceal his arms and habiliments, with provision for twenty-four hours, as to appear a common traveller; by which means a considerable body might be admitted into a town, one at a time, unsuspected, and, afterwards assembling, surprise it. I told him I was not a military man, of course no judge of such matters, and advised him to apply to the Bureau de la Guerre. He said he had no friends, and so could procure no attention. The number of wild schemes proposed to me is so great, and they have heretofore taken so much of my time, that I begin to reject all, though possibly some of them may be worth notice.
"Received a parcel from an unknown philosopher, who submits to my consideration a memoir on the subject of elementary fire, containing experiments in a dark chamber. It seems to be well written, and is in English, with a little tincture of French idiom. I wish to see the experiments' without which I cannot well judge of it."
This "unknown philosopher" was ascertained to be Marat, afterwards of notorious memory. At this time he was devoted to philosophical studies, and he wrote several treatises on light, heat, and electricity, which are praised by his biographers for their matter and style. He occasionally invited Dr. Franklin, and other men of science, to see his experiments.