Astronomer, physicist, and optician.

Garde du cabinet de physique et d’optique du roi at the château de la Muette in Passy (1774). Invented a micrometer that could measure the diameter of celestial bodies and the distances between them with great accuracy (1777).

Franklin was one of five members of the committee assembled to settle the dispute between Rochon and Le Roy over the lightening rods at the château de la Muette (1779).

Rochon's discussions with Franklin about a copying method Franklin had earlier devised in America inspired him to perfect Franklin’s method and to invent a machine that could mechanically engrave type (1780).