Pierre-Isaac POISSONNIER (1720-1798). Manuscript signed "Poissonnier Conseiller d'Etat, medecin consultant du Roy", Mémoire sur une Méthode facile et assurée de rendre l'eau de mer potable, [circa 1765]; large folio of 11 pages bound with a blue ribbon (small cracks at fold). Poissonnier recalls the importance of having potable water on a ship, and lists the various processes invented before him, up to and including that of the English chemist Appleby using the "cautery stone". He then describes and details the operation of his own "distillation machine" (with cross-references to plates, not attached), which has been tried and tested "on more than 60 vessels, both Royal and commercial", and in particular "on ships destined for the Negro trade"...