[Charles CAGNIARD DE LATOUR (1777-1859) engineer and physicist.] Manuscript, Œuvres complètes, observations, découvertes et inventions...., [1872]; one vol. in-4, cherry half-bassoon (period binding; small accident at one corner). Precious collection of the works of this inventor, with a biographical note. The title of the collection is: Œuvres complètes, observations, découvertes et inventions de Mr. le baron Cagnard [sic] de La Tour [...] précédées d'une notice biographique et ornée de son portrait. This collection is all the more important as there is no printed treatise by the author, apart from a few memoirs published in scientific periodicals (in particular the Compte-rendus de l'Académie des sciences), which have been published in offprints, which are in any case rare. A physicist and engineer from the first class of the École Polytechnique (that of the year III), Cagniard de Latour then joined the corps of engineer-geographers, became auditor of second class at the Conseil d'Etat (1810) and was assigned to the administration of powders in 1811. He became an auditor of the first class for the Minister of the Interior in 1812 and 1813, and also an auditor for the Commission of Petitions in 1813. But he left these activities of civil servant rather quickly to devote himself entirely to his research in fields as diverse as mechanics, chemistry, physics and acoustics. It is especially in this last field that he became famous: seeking to produce a standard for the pitch of sounds based on a determined frequency, he developed in 1819 the siren known as Cagniard-Latour: by controlling the speed of rotation, this instrument allows to produce at will a sound of calculable and adjustable frequency. It was he who gave the name "siren" to this device, which has since been used universally, in reference to the sirens of Greek mythology. He later used this device to study the propagation of sound in liquids. The set presented here was composed after the baron's death, in order to gather his main research and inventions. This manuscript was written in a neat and regular handwriting, on the front of the pages. It is presented in two parts: I. Illustrations of the work. Notice on the life, works, discoveries and inventions of Monsieur le Baron Cagnard de Latour (33 ff.), biographical note. - II. Baron Cagnard de Latour, member of the Academy of Sciences. His life, his works, his discoveries (428 ff.). This part presents the inventions and studies of the baron, notably the famous mermaid. Almost everything is written in the third person: it is an analytical memoir based on his works. At the end, however, the few printed memoirs mentioned at the beginning of this sheet have been reproduced: - Memoir on a conservoid plant of a new species. Extract from a memoir presented to the Académie des sciences on May 11, 1835 (and published in the Annales des sciences naturelles, July 1835, ff. 371-382). - Memoir on wine fermentation, presented to the Académie des sciences on June 12, 1837 (ff. 383-399). - Report to the Institut de France, March 12, 1810, on a pump presented by M. Cagniard de Latour (ff. 414-417). - Report on observations and experiments made on the cause and effects of wine fermentation. Extract from the minutes of the sessions of the Academy of Sciences, 23 July 1838 (ff. 418-426). On the other hand, no portrait appears in our copy, in spite of the title's announcement; similarly, the plate illustrating the first dissertation in the print has not been reproduced. Copy of the baron du Charmel (bookplate): this is Oscar de Bonnefoy du Charmel (1813-1898), Cagniard's son-in-law (he had married his only daughter Philippine, 1824-1886). It is him who probably gathered all the writings of his father-in-law.