A Clock for the Ages: Potassium Argon, Garniss H. Curtis, _National
Geographic Magazine_, 120: 590 (October 1961).
Exploring 1,750,000 Years into Man’s Past, L. S. B. Leakey, _National
Geographic Magazine_, 120: 564 (October 1961).
Five-Billion-Year Clock, Patrick M. Hurley, _Saturday Evening Post_,
234: 26 (March 18, 1961).
Geologic Time Scale, J. Laurence Kulp, _Science_, 133: 1105 (April 14,
1961).
Geology, Reginald A. Daly, _Scientific American_, 183: 36 (September
1950).
Tracks of Charged Particles in Solids, R. L. Fleischer, P. B. Price, and
R. M. Walker, _Science_, 149: 383 (July 23, 1965).
How Old Is It?, Lyman J. Briggs and Kenneth F. Weaver, _National
Geographic Magazine_, 114: 234 (August 1958).
Moving Picture of the Last Ice Age, Richard Foster Flint, _Natural
History_, 66: 188 (April 1957).
Modern Methods for Measurement of Geologic Time, E. J. Zeller, _Mineral
Information Service_, 18: 9 (January 1965). Single copies are $0.10
from Division of Mines and Geology, Ferry-Building, San Francisco,
California 94111.
Fluted Projectile Points: Their Age and Dispersion, C. Vance Haynes,
Jr., _Science_, 145: 1408 (September 25, 1964).
Unraveling the Age of Earth and Man, E. L. Simons, _Natural History_,
76: 52 (February 1967).
Radiocarbon Dating and Archeology in North America, F. Johnson,
_Science_, 155: 165 (January 13, 1967).
Fission-track Dating of Bed I, Olduvai Gorge, R. L. Fleischer and
others, _Science_, 146: 72 (April 2, 1965).
Lead Isotopes and the Age of the Earth, G. R. Tilton and R. H. Steiger,
_Science_, 150: 1805 (December 31, 1965).
Strontium-Rubidium Age of an Iron Meteorite, G. J. Wasserburg and
others, _Science_, 150: 1814 (December 31, 1965).
[Illustration: THE COVER]
U. S. Geological Survey scientists prepare acetylene gas, made from the
carbon-14 in a geological specimen, in a vacuum line. This gas will be
fed into a proportional counter to determine the age of the specimen
by its ¹⁴C count. (See “Carbon-14 Counting” beginning on page 12.)
[Illustration: THE AUTHOR]
Geophysicist Henry Faul, an authority on nuclear dating, is professor of
Geophysics and chairman of the Department of Geology at the University
of Pennsylvania, Philadelphia. He holds a doctoral degree from the
Massachusetts Institute of Technology, and has taught at the
Universities of Strasbourg and Bern in Europe. Dr. Faul was a
geophysicist with the Manhattan Project during World War II, and was
formerly chief of the Radiation Laboratory, U. S. Geological Survey,
Denver, Colorado. For many years he was engaged in geological age
determination work with the Geological Survey and the Carnegie
Institution of Washington in Washington, D. C.