RT Journal Article SR Electronic T1 The thermal state of the earth JF American Journal of Science JO Am J Sci FD American Journal of Science SP 825 OP 835 DO 10.2475/ajs.239.11.825 VO 239 IS 11 A1 Harold Jeffreys YR 1941 UL http://www.ajsonline.org/content/239/11/825.abstract AB "The available data related to the internal heat of the earth are reviewed. From these considerations it is concluded that: (1) The average radioactivities of surface rocks show a steady decrease with increase of density, though there is much scatter within a given type. (2) Heat generated at depths up to 300 km. or so has had sufficient time to approach a state where it is conducted out as rapidly as it is produced. (3) Nothing in the new results encourages the hope that fusion temperatures are a normal feature at any depth within the crust. (4) The thermal contraction available for mountain formation remains essentially unchanged except that a more uniform rate is suggested."