576 
GEOPHYSICS: L. A. BAUER 
Proc. N. a. S. 
"The results obtained in these investigations have suggested a theory, which both 
accounts for many of the more important phenomena of thunderstorms, and relates 
them to those of fine-weather atmospheric electricity and terrestrial magnetism .... 
"The order of magnitude of the currents in thunderstorms, as indicated by the 
results of observations of lightning discharges, is such as to suggest the possibility of 
correlating the phenomena of atmospheric electricity with those of terrestrial 
magnetism." 
5. Magnetic Storms, Polar Lights and Earth Currents: Many problems 
of interest to several sciences come under this head. The various pro- 
nounced manifestations of solar activity and terrestrial magnetic and 
electric activity during the past month, especially March 22-23, have 
called renewed attention to these problems. The magnetic disturbance 
of March 22-23 was world-wide and was one of the severest recorded. 
On the evening of March 22 one of the most remarkable displays of the 
Aurora Borealis was witnessed at Washington and at points in even lower 
latitudes; at a corresponding time there was a fine display of the Aurora 
Australis at the magnetic observatory of the Department of Terrestrial 
Magnetism at Watheroo, Western Australia. During the magnetic 
disturbances and auroral displays the generated earth-currents caused 
interruptions on cable and telegraph lines. The sun-spot activity during 
this period was of a very marked and interesting character. Dr. Abbot 
reported that the solar constant, as observed by the Smithsonian Institu- 
tion party at Calama, Chile, on March 23, had reached the low value of 
1 . 866, whereas from January 1 to March 22 it had varied from 1 . 93 to 
2.00; on March 24, the value was 1 .905, and thereafter it went up again. 
This case illustrates well the joint interest of various sciences. 
The general effect of magnetic disturbances is to diminish for a time 
the intensity of magnetization of the earth's field, in severe cases as much 
as ten percent. It took about three months after the severest magnetic 
storm on record, the one of September 26, 1909, before the earth's mag- 
netic intensity had returned to its approximate normal value. An in- 
teresting theory^ of magnetic storms has recently been advanced by Prof. 
F. A. Lindemann, director of the Department of Physics at the Univeristy 
of Oxford. To overcome some of the difficulties of Dr. Chapman's theory^ 
of a stream of charged particles, Lindemann suggests the alternative of 
clouds of ionized gas ejected from the Sun and driven away by light- 
pressure. Such a cloud would be completely ionized, and therefore in- 
visible; it would be kept generally together because it contains both posi- 
tive and negative ions; and yet it would expand sufficiently to satisfy 
observed facts about the duration of magnetic storms as the earth passes 
through the cloud — in our upper atmosphere the ions would recombine 
and cause the storm. The theory is worked out quantitatively and found 
to satisfy known facts. 
6. Magnetic and Electric Observations During Solar Eclipses: Intensive 
observations under this head have been made, especially since the total 
