332 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
in Our Atomic Age.” Three days later a cable from Dr. W. F. Libby 
of the United States Atomic Energy Commission gave advance source 
details of an underground explosion that was carried out in Nevada 
on September 19. This advance news greatly excited the seismologists 
gathered at Toronto who made hurried endeavors to have the seismic 
waves from the explosion as well recorded as possible. 
Actually, the waves that went into the ground from the explosion 
turned out to be relatively small, and, generally speaking, were re- 
corded only in Western United States at distances up to about 700 
miles. There were, however, recordings by special field instruments 
which had been set up for the purpose in Mexico at a distance of 1,400 
miles, and by a very sensitive seismograph in Alaska, 2,300 miles away. 
Doubt remains as to whether the more distant recordings would have 
been identified as waves from a nuclear explosion if the source data 
had not been released. From the seismic point of view, the explosion 
was principally useful in supplying further information on crustal 
structure in Western United States. 
Seismologists hope that in due course it will be possible to utilize 
nuclear explosions to sharpen many of their inferences on the earth’s 
interior. At the same time, seismologists appreciate that all such 
controlled experiments that are carried out at their instigation must 
be subject to total scrutiny on the score of human welfare, genetical 
and otherwise. 
Earthquakes and atom bombs both have great potentialities as de- 
structive agents. But both can, nevertheless, be turned to great 
advantage in enabling us to understand the properties of our planet 
earth. 
REFERENCES 
Bates, D. R. (Editor). 
1957. The planet earth. London. (Includes discussions, written for the 
lay reader, on various aspects of the earth’s interior.) 
BULLEN, K. E. 
1953. Introduction to the theory of seismology. 2d ed. Cambridge Uni- 
versity Press. (Contains a mathematical discussion of seismic 
waves in relation to the earth’s interior. ) 
1954. Seismology. London. (A briefer and less advaneed account of 
seismic waves and the earth’s interior.) 
JEFFREYS, Sir H. 
1950. Earthquakes and mountains. London. (An account written for the 
layman.) 
1952. The earth. 3d ed. Cambridge University Press. (An advanced ac- 
count of the problems of the earth’s interior.) 
