SUNSPOTS— ANDREWS 139 



parent solar surface by solar latitudes 6° and 40°, the one in the 

 Northern Hemisphere, the other in the Southern, spots but rarely 

 occur. The first spots of a new outburst of solar activity appear 

 near the high latitudes of the belts, and, as the cycle progresses 

 toward maximum spottedness, the average latitude of these dis- 

 turbances progresses constantly toward the lower solar latitudes, 

 reaching the value of 15° at maximum, and continuing onward 

 toward the lower limits of the belts as the cycle declines toward 

 minimum. Thereafter the first evidence of a new cycle is the reap- 

 pearance of spots near the upper limits of the belts. The causes 

 of this behavior of spots, as well as of the variations of their mag- 

 netic properties, are still clothed in mystery. 



The aim of this article is, however, not to recount the properties 

 of sunspots as such. Given this manifestation of solar activity, our 

 interest lies in the determination of any possible terrestrial influence. 

 The presence of huge magnetic fields in sunspots results in their 

 acting as howitzers to pour forth charged particles of matter into 

 the interplanetary realm. If the earth is in the range of the how- 

 itzer, its atmosphere is the recipient of these particles, and, beyond 

 doubt, electrical phenomena should occur there. The lotation of the 

 sun on its axis in a period of some 25 days prevents the earth's 

 being constantly in the range of a sunspot or sunspot group, and 

 so we look for the evidence of a terrestrial effect primarily when a 

 spot lies near the center of the sun as seen from the earth. When 

 this state of affairs is valid, such terrestrial phenomena as auroral 

 displays, magnetic storms, and effects on long distance radio reception 

 should occur, for they all depend upon the electrical conditions of 

 the atmosphere ; and indeed our expectations are fulfilled. All three 

 phenomena show a close correlation with sunspot activity and par- 

 ticularly with the passage of an active sunspot group across the 

 central area of the sun's disk; the aurorae, borealis and australis. 

 perform beautifully, magnetic compasses oscillate to and fro over 

 a small amplitude centered at their normal position, and long dis- 

 tance radio reception is either improved or hampered. In connection 

 with the last of these it should be said that whether reception is 

 improved or hampered depends upon the wave length of the signals 

 and other factors related to radio transmission. 



The assumed validity of a correlation of electrical phenomena on 

 the earth and sunspot activity is thus established in a straight-fur- 

 ward manner. The many additional correlations, including the cor- 

 relation of sunspot activity with weather conditions, the receipt of 

 rabbit pelts, wars, floods, international crises, economic tranquillity 

 and distress, the growth of trees, even with volcanic activity, hardly 

 fall, however, within the category of terrestrial electrical phenomena. 



