Jeffreys, Sir Harold (1891-1989), a British geophysicist, became a leading authority on Earth’s interior. He set forth his ideas in his book The Earth: Its Origin, History, and Physical Constitution (1924). He provided the theory for the modern method of exploring the interior of the planet by means of seismic waves (vibrations of rock) created by explosions near the surface (see Seismology ). This technique is used in prospecting for oil and gas. Jeffreys also wrote books on the scientific method and on mathematical physics.
Jeffreys was born on April 22, 1891, in Fatfield, near Durham, England, and educated at Cambridge University. From 1946 to 1958, he was Plumian professor of astronomy and experimental philosophy at Cambridge. Jeffreys was knighted in 1953. He died in Cambridge on March 18, 1989.
