Hachette had been taught by Monge in Mézières. As a young man, he sent some papers on applied geometry to Monge, leading to an appointment alongside him, teaching descriptive geometry to students who included Poisson, Arago and Fresnel. Hachette had previously fought against the Austrian army with Guyton de Morveau (in the first battle to employ aerial surveillance). As Monge’s one-time protégé, his notable advancement of the subject included the continuation of Monge’s work. Faraday and Davy visited him during their two-year European journey, Faraday maintaining the connection back in London.