Becquerel asserts his priority over Faraday in the discovery of the magnetic properties of air. Edmond Becquerel, French physicist (1820–1891) credited with the discovery of the photovoltaic effect. Handwritten manuscript in English and French by Edmond Becquerel (plus five lines in the hand of his son, Henri Becquerel), four pages on two adjoining sheets, 7 x 9, asserting his priority over Michael Faraday in the discovery of the magnetic properties of air. Becquerel presents Faraday’s publications on the magnetism of oxygen and the priority of discoveries, transcribing in English and translating into French passages from Faraday’s memoir, ‘On the Diamagnetic Conditions of Flame and Gases.’ In part: “So oxygen appears to be magnetic in common air. Whether it be really so or only less diamagnetic than air (a mixture of oxygen and nitrogen), we shall be better able to consider hereafter…Now, until it is distinguished, we cannot tell which gaseous bodies will rank as diamagnetic and which as magnetic.” Becquerel writes that he did not know of Faraday’s publications before having published his two memoirs (May 1849 and August 1850) and that his own research has shown that oxygen is strongly magnetic. At the conclusion, Henri Becquerel pens five lines stating that Faraday’s work is later than that of Edmond Becquerel. In fine condition, with some faint staining and a rough bottom edge. Accompanied by three contemporary French translations of letters penned in a secretarial hand, circa 1850-51, copying two letters by Faraday and one by Herschel.