Vol. 6, 1920 
GEOPHYSICS: C. F. MARVIN 
561 
Although the various seismological problems have been, for conven- 
ience, classified into three groups, it must not be inferred that they are 
sharply defined and distinct; each group will contribute to the problems 
of the others. Instruments that are primarily intended for world-wide 
problems will yield information bearing on local problems in their neigh- 
borhood; and instruments meant for local problems will also record the 
world-shaking earthquakes. 
Relations to Other Sections of Geophysical Science 
For convenience we divide science into branches, influenced largely 
by differences in the methods used. But nature knows no such dividing 
lines; and we find that many problems can be solved only by the co- 
operation of several branches. This is especially true of the geophysical 
sciences. The special section of seismology looks to all the other sections 
for help; to geodesy to determine the slow earth movements, horizontal 
or vertical, that lead up to earthquakes, and the sudden movements 
that take place at the time of the shock ; to meteorology to tell us the atmos- 
pheric conditions when microseisms are prevalent; to physical oceanog- 
raphy for information about the deeps of the oceans, along whose borders 
submarine shocks are common. 
The independence of earthquakes and volcanoes has been strongly 
emphasized during the last thirty years, because nearly all the strong 
earthquakes were unaccompanied by volcanic phenomena of any kind; 
and, on the other hand, the great volcanic outbursts, such as Krakatoa 
in 1883 and Mt. Pelee in 1902, caused only insignificant earth tremors. 
These facts cannot be contraverted ; and still we must not forget that the 
volcanic belts lie in or near the great earthquake zones; and there may 
be some common cause of both classes of phenomena. 
The influence of earthquakes on suspended magnets may be assigned, 
with much confidence, merely to the mechanical vibrations. But may not 
the altered state of strain, in the neighborhood of the generating fault, 
change the magnetic condition of the rock there if the rock contains mag- 
netic minerals, so that the general magnetic field might be modified? Or 
may not the passage of violent earthquake waves through magnetic rock 
alter its magnetization, especially if that magnetization was assumed at 
some time when the earth's field was different from what it now is? 
Seismology does not ask without giving. It can contribute its conclu- 
sions to the other brancbes of science and help them in the solution of 
their problems. 
THE STATUS AND PROBLEMS OF METEOROLOGY 
By C. F. Marvin 
Meteorology is one of those sciences which developed on the side of 
practical application for the welfare of mankind to a far greater extent 
