Jean-Baptiste SAY (1767–1832). Letter from the author, Paris, October 13, 1822, to a colleague; 1 page, in-4. He recommends Claude Burdin to him, “a mining engineer in Saint-Étienne […] He is the inventor of a new process for harnessing the power of waterfalls and would very much like the Academy of Sciences to take note of it; and he cannot find a better patron than you”… Enclosed is a letter from the author, Paris, February 22, to a friend (1/2 page, folio) regarding a mechanical carding machine that has been proposed to him; he would like to know whether this method can be put to good use…