An Original Handwritten Autograph Letter signed by Irish Scientist John Tyndall to Fellow Scientist Sir Henry Enfield Roscoe. Undated. A letter about an election of a fellow friend to the Athenaeum Committee. John Tyndall 1820 – 1893 was an Irish physicist and chemist. His scientific fame arose in the 1850s from his study of diamagnetism. Later he made discoveries in the realms of infrared radiation and the physical properties of air, proving the connection between atmospheric CO2 and what is now known as the greenhouse effect in 1859. Tyndall also published more than a dozen science books which brought state-of-the-art 19th century experimental physics to a wide audience. From 1853 to 1887 he was professor of physics at the Royal Institution of Great Britain in London. He was elected as a member to the American Philosophical Society in 1868. Sir Henry Enfield Roscoe 1833 – 1915 was a British chemist. He is particularly noted for early work on vanadium, photochemical studies, and his assistance in creating Oxo (food), in its earlier liquid form. Size is 115mm x 90mm. Condition is good.