Bulletin 54. Geophysical Methods of Exploration and their ...

GEOPHYSICS DEFINED 15
ately their positions even in heavy fogs. A_still more recent deveIopmcnt
has been the improvenleut of submarine detectors as vital
defense i_struments through oceanographic research. Another
branch of geophysics deals with terrestrial electricity and magnetism
and such terrestrial and extrn-terrestrial phe_mmena as
sun spots and cosmic showers and their effects on the earth and
our everyday activities. It has been fouud for instance that solar
disturbances arc apt to disrupt telephone, telegraph and radio
communications, and eve1* ruin the satisfactory operation of teletype
machines. Again, it has been found that aeroplanes flyil_g
over certab_ areas, as in that portion of New Jersey adjacent to
Wilmington, Delaware, cannot rely upon their co_upasscs due to
lhe strong mag_mtic disturba_lce in that area. Other areas have
bee_ fomld in which morked radio disturbances are always obtained.
The study of all these varied phenomenon comes under
this branch of geophysics.
(_eodcsy is another branch of geophysics devoted, to the study
of the shape of the earth and in detail it gives us tl_c general
configuration and elevation of the country. Seisnmlogy deals with
earthquakes, their poi_tts of origin, severity and other related
facts which it is necessary to know in making studies as to how
to minimize their danmgc, determine their possible periodicity and
otlmr vital data. VulcauoIogy is a branch devoted entirely to the
study of volcanoes, a_d there arc still other branches of geophysics
which effect our lives in varying degrees.
The examples cited serve not only to show the wide fle]d embraced
by the term geopllysies, but also to show that the various
b_'a_chcs are all part o_ the general study of the earth and as
such also come under the head of gcology, the science devoted
to the study of the earth.
APPLICATION OF _EOPI[YSICS TO GEOLOGIC)tL RESEARCII
Although it might appear from the above definitions that meteorology,
oceanography, hydrology, scis_Lmlogy, w_lc_mology,
geodesy, terrestrial a_ag_etisJa and electricity are all a part of
geology, this co_ecpt is not in accordance with that generally
held by the layman. He thiaks of geology as a science devoted
eutirely to the study of rocks a_d mit_erals and of maps slmwing
the distrlbutio_ of these rocks and minerals. The commonly
accepted idea of a geologist is a man wearing boots who goes
around chipping off specimens of rock with a hammer; his studies
are limited to the rocks he can see and get specimens of, and
althol_gh in a vague sort of way it is understood that he has some
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