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Two volumes bound in one. [4], xiv, [2], 275, [1 blank]; viii, 164 pp. 11 engraved folding plates at the rear of the first work. (4to) 25x19 cm (9¾x7¾") later full mottled calf, spine gilt, all edges red. First Editions.

A pair of rare works by the great French scientist and watchmaker. Berthoud held the position of Horologist-Mechanic by appointment to the King and the Navy, and left behind him an exceptionally broad body of work, in particular in the field of marine chronometers. The first work is a treatise detailing all the parts required for the building of a sea clock. It helped to seal the reputation of Berthoud’s skill, in particular with respect to his competitors in longitude at sea research, such as Harrison and Pierre Le Roy. The second work is a response to an earlier treatise by Le Roy, evidence of their intense commercial rivalry.