Nicolas-Mathieu Rieussec

Nicolas-Mathieu Rieussec was a Paris watchmaker credited with constructing, in 1821, a timing instrument used to record the results of horse races at the Champ de Mars in Paris, using a rotating dial and an ink-marking pen to record elapsed time — the device from which the term 'chronograph' (writer of time) derives, since it literally marked its readings in ink rather than merely displaying them on a dial.

Rieussec's instrument was presented to the French Academy of Sciences and is documented in period accounts as a genuinely novel solution to the practical problem of timing an event whose exact end could not be anticipated, a distinct technical challenge from ordinary timekeeping. It predates the reset-to-zero chronograph mechanisms later patented by Adolphe Nicole and Jules Capt in 1862, which made the chronograph practical for repeated everyday use rather than a specialised, single-purpose recording instrument.

Rieussec's name has been commercially revived by later watch brands, and this encyclopedia treats the historical 1821 timing device and any modern product using his name as related but distinct subjects, consistent with its treatment of other historic maker names later revived commercially.