Abstract

Chemistry was the poor relation in the education of Polytechniciens in Poincaré’s time and therefore was not one of the scientist’s centres of interests despite the social importance it took on at the end of the 19th century. In 1907 the mathematician, physicist and philosopher encountered it rather fortuitously in his role as the chairman of the Scientific Commission tasked with the study of gun propellants set up following the explosion of the battleship Iéna. He was asked to take on this role because the eminent specialist in gunpowder and explosives Marcellin Berthelot who had initially been asked to be chairman had passed away. The catastrophic explosion of the battleship accident dealt a severe blow to the country’s confidence in its means of defence in a tense international context between France and Germany following the 1871 annexation of Alsace-Lorraine and at a time when the Moroccan crisis was rekindling a desire for revenge. The government decided that Poincaré alone had the scientific authority to reassure the public about the safety of the smokeless chemical powders invented by his classmates at Polytechnique Paul Vieille and thus to keep the enemy at bay. The Commission’s archives and Poincaré’s own administrative correspondence demonstrate his commitment to this issue. His personal correspondence with Henry Le Chatelier, another X-Mines engineer who specialised in gunpowder and explosives, gives a clearer view of his understanding of the complex issues linked to the new types of gunpowder. It also reveals his strategy for overcoming the institutional obstacles caused by the rivalry between the Poudres et Salpêtres production department and the French Artillery and Navy and also by attacks on the gunpowder monopoly from industrialists and their supporters in the French Parlement.