Sir William Ramsay, Scottish chemist, c 1910-1920.

UNITED KINGDOM - JUNE 10: Photogravure by Emery Walker of Sir William Ramsay (1852-1916). Ramsay was professor of Chemistry in Bristol (1880-87) and at University College London (1887-1913). He is best known for his discovery of the noble (inert) gases helium, neon, argon, krypton and xenon, for which he was awarded the Nobel Prize for Chemistry in 1904. In 1894, together with Lord Rayleigh (1842-1919), he discovered the rare gas argon, followed in 1898 by helium, neon, krypton and xenon. Ramsay also made important contributions to thermodynamics and stoichiometry, and was the only man to discover a complete Periodic Group of elements. He was knighted in 1902. (Photo by SSPL/Getty Images)