THE SUN AND SUNSPOTS MAUNDER 165 



Another feature is suggested by this diagram, but will be better 

 brought out in a different connection. It is that the southern hemi- 

 sphere appears to encroach slightly on the northern at the equator, 

 or at about the time of the close of one cycle and the beginning of the 

 next. The southern influence seems to cross the equator. 



Since the origin of the solar spots lies within the sun, and the 

 northern and southern spots show differences in their behavior, we 

 must conclude that the sun is not symmetrical in the constitution of 

 its interior. If then we assume, as the basis of any investigation, 

 that the sun is symmetrical in its internal constitution, we are making 

 an assumption contrary to the evidence supplied by the behavior of 

 its surface. 



If there be this clear distinction between the two hemispheres, is it 

 possible that one of them might go out of action for a time, and if so, 

 what would follow ? 



This is not a mere oratorical question; the event supposed has 

 actually occurred. Dr. Rudolf Wolf, of Zurich, demonstrated, and 

 Spoerer developed that demonstration further, that in the latter part 

 of the seventeenth century and the beginning of the eighteenth the 

 northern hemisphere of the sun failed for many years to produce a 

 single recorded spot. 



Was there any effect during that same period recognized here on 

 the earth that could be plausibly associated with this failure in spot 

 production in the sun's northern hemisphere? 



It is suggestive that, while the northern hemisphere was thus en- 

 tirely barren, the southern hemisphere of the sun had some spots, but 

 only few, and for nearly 70 years the sun showed a prolonged spot 

 minimum. The failure in spot activity of the northern hemisphere 

 was not compensated by an increased activity in the southern. 

 Further, as Miss Agnes Clerke pointed out in Knowledge for Sep- 

 tember, 1894, no aurorae were reported during these years; from 

 which we may infer that there were no great magnetic disturbances 

 taking place, on the earth. It is also suggestive that Prof. A. E. 

 Douglass, who has been studying with great particularity the annual 

 rings of trees in relation to climate and the solar activity (Climatic 

 Cycles and Tree Growths) , found that this same period " was the 

 interval in the yellow pines" (i. e. of northern Arizona) "which 

 gave me more trouble than any other in trying to work out the action 

 of the sun-spot cycle" (Journal of the British Astronomical Asso- 

 ciation, 32, 223). Professor Douglass added that it seemed to him 

 " a very important corroboration of the relationship between solar 

 activity and terrestrial conditions, for I presume that these tree 

 variations are related directly to the weather." 



