French physicist (1859-1906) best known for his pioneering investigation of radioactivity, who shared the 1903 Nobel Prize in Physics with his wife, Marie Curie. ALS in French, signed “P. Curie,” two pages, 5.25 x 8.25, Faculte des Sciences de Paris letterhead, April 1, 1906. Letter with important scientific content referring to radiation. In part (translated): "My collaborator Mr. Labarde boiled the water from the bottles you had the kindness to send us. The gases we have extracted during the ebullition have been examined under radioactive point of view. They do not contain radium emanation." Curie further congratulates his correspondent for his clear-sightedness on a pathetic and revolting affair, before concluding, saying: "I am one of those who read the articles so clear and so precise." In fine condition, with staining along the top edge. Pierre Curie’s letters are very rare, especially with such significant scientific content.