136 BAUER— SOLAR ACTIVITY AND [April 23. 



around the globe, and as shown to be necessary to account for the 

 actual disturbance effects. Hence the direction test already excludes 

 the possibility of ascribing certain of our magnetic storms, at least, 

 to the effect of negatively electrified particles and cathode rays 

 received from the sun. In a similar manner, it can be shown that 

 positively electrified particles would likewise not accomplish the de- 

 sired result. 



But the time required for the quickest disturbances to get around 

 the earth — about 3^ to 4 minutes — furnishes another crucial test. 

 Knowing the electric charge carried by the particles, their velocity, 

 and the deflecting effect of the earth's magnetism, it is possible to 

 compute the radius of the circle around which they would have to 

 move were they to come to the earth approximately, for example, in 

 the plane of the equator and accomplish the circuit in 3^ minutes. 

 This radius turns out to be 580 times that of the earth's radius. 

 Hence, these particles could never approach the earth closer than 

 2,300,000 miles! And if we compute the strength of the current 

 necessary to produce at that distance even one of these comparatively 

 minute magnetic disturbances, we find it would have to be on the 

 order of 60,000,000 amperes, or six:ty times that deemed sufficient to 

 account for the big disturbances. We are accordingly forced to look 

 elsewhere for the chief source of our magnetic storms. [The value 

 of the radius, 2,300,000 miles above given applies to an electronic 

 mass. Where we to increase the latter 1,000,000 times the radius 

 would still be 23,000 miles. K we take the mass of the carrier of 

 the electric charge the size of that of a particle brought to us by 

 the pressure of light, the radius turns out less than that of the earth, 

 hence an impossible result.] 



In addition to negatively electrified particles coming from the 

 sun, we also receive radiations such as the gamma rays of radium or 

 the Rontgen rays, which are not deflected by the earth's magnetic 

 field as they do not carry electric charges. Their chief effect would 

 be to ionize the gases of which the atmosphere is composed, i. e., 

 make these gases better conductors of electricity. Ultra-violet light 

 has the same effect. Now we know that a small part of the 

 magnetic forces acting on a compass needle is due, not to magnetiza- 

 tions or electric currents below the earth's surface, but to electric 



