The English geologist Arthur Holmes (1890-1965) was a pioneer in geochronology, a gifted petrologist, and a lucid expositor of the physics and history of the earth's outer layers.

Arthur Holmes was born on Jan. 14, 1890, at Hebburn-on-Tyne. At school he became interested in the age of the earth through reading Lord Kelvin's Addresses. Winning a scholarship to London's Imperial College, he graduated in geology and physics in 1911 and immediately began research on the radioactivity of rocks, guided by R. J. Strutt (later 4th Baron Rayleigh). Strutt's studies had revealed a source of heat within the earth, unsuspected when Kelvin made his estimate that not more than 40 million years had elapsed since the earth's crust had solidified from the molten state. Holmes shared with Strutt in overthrowing this conclusion, and he made successive advances toward establishing a new and much longer geological time scale, eventually showing the earth to be...