26 
GEOPHYSICS: L. A. BAUER 
radiation plays the prominent part required in the Schuster analysis of 
the diurnal variation of the earth's magnetism, the question naturally 
arises: If, at any particular moment or period, the solar radiation fall- 
ing upon the earth's atmosphere, suffers, from some cause, an appre- 
ciable increase or decrease, is there a corresponding observable magnetic 
change? A diminution, for example, in the amount of solar radiation, 
could be caused by the interposition of some screening body between 
the sun and the earth. The interposing body might be the moon, as 
during a total solar eclipse, or a cooling layer above the sun's photo- 
sphere. In the first case, magnetic observations made during a total 
solar eclipse would shed some light, and in the second case a compari- 
son of observed values of the solar constant with concomitant magnetic 
records would be of great interest. We have carried out both lines of 
inquiry. 
It is not possible to enter here into the details of all tests applied and 
as to methods of computation employed. It must sufiice to state the 
chief conclusions derived to date. 
a. Changes in the earth's magnetism of appreciable amount are found 
associated with the changes in solar radiation as shown by values of the 
solar constant possessing the requisite accuracy. For the average daily 
change in the solar constant, which amounts to about 1.5% of its value, 
the magnetic constant, used as a measure of the prevailing magnetic 
state of the earth, suffers a change of about 0.003%, or about one digit 
in the fifth decimal C. G. S. units. The effect on the horizontal compo- 
nent of the earth's magnetic force would be about twice this. 
b. Decreased solar constant appears to be accompanied by increased 
magnetic constant and decreased diurnal range of the earth's magne- 
tism, in accordance with the following relations: 1% change in the solar 
constant is accompanied by a change of about 0.002% in the magnetic 
constant, and by about 1% in the magnetic diurnal range. Assuming 
for the present a linear relation between the solar-constant and mag- 
netic changes, a 10% change in the solar constant, as occasionally 
occurs, may be accompanied by a change in the magnetic constant of 
about 0.02%, and by about 10% in the magnetic diurnal range. The 
magnetic effects observed during total solar eclipses are about equiva- 
lent to those which might be expected from about a 10% change in the 
intensity of solar radiation. 
c. Since the changes in solar radiation are aperiodic and occur more 
or less spontaneously, the effect on the earth's magnetism is generally 
of a threefold character: (1) An alteration in the diurnal range, (2) 
perturbations both of the world-wide and the local kinds, (3) an out- 
