Abstract :
DURING the great magnetic storm of April 1938 energy was expended at the rate of two billion kilowatts for a two-hour interval. Couched in more comprehensible terms, this is 100 times the capacity of all the hydroelectric developments in the United States and 4 times the estimated potential developments of the entire world. The magnetic storm of March 1939, which produced so much disturbance on power and communication lines, seems to have been greater than the 1938 storm; possibly it is the greatest ever recorded.
