Autograph Letter Signed ‘Edmond Becquerel’, to Monsieur Boutigny [Pierre Hippolyte Boutigny, professor of chemistry], apparently inviting him to witness experiments with sulphuric acid (based on Boutigny’s work) to be undertaken by Becquerel’s father at the botanical gardens. In French. A good one page example 8 x 6 inches, integral address leaf, tipped on to an old album leaf. 18 October 1850. Uncommon. Alexandre-Edmond Becquerel (1820-1891) was a French physicist who studied the solar spectrum, magnetism, electricity, and optics. He is known for his work in luminescence and phosphorescence. He discovered the photovoltaic effect, which is the physics behind the solar cell, in 1839. He was the son of Antoine César Becquerel and the father of Henri Becquerel.