THE SUN AND SUNSPOTS MAUNDER 



161 



area of the sun; the total mean spotted area of the northern 

 hemisphere being shown separately from that of the southern. 

 The principal feature of the diagram therefore is the comparison of 

 the sun-spot areas in the two hemispheres. From this point of 

 view the diagram is worth careful consideration. Just as the first 

 illustration showed that during the years represented there was only 

 one sun-spot cycle — a cycle having a mean duration of about 11% 

 years — so the present diagram shows that the cycle holds good for 

 each hemisphere, as well as for both together. The solar cycle is one. 

 There is no question of the existence of submultiple cycles, or of 

 incommensurable cycles of greater length. 



Fig. 2. — Mean daily spotted area, north and south, 1874-1923 



Further examination of the diagram shows that the maximum 

 activity in any particular cycle does not necessarily fall at the same 

 epoch for the two hemispheres ; rather, a divergency appears between 

 them. In each of the four cycles represented, the northern activity 

 was developed before the southern ; in each of them the curve in one 

 hemisphere attained a single crest, while in the other it attained a 

 double one; or, to put it in other words, the form of the curve was 

 not the same in the two hemispheres. We have therefore here a 

 solar dichotomy displayed. Had the results of the whole century 

 been presented in a like form, other peculiarities would have been 

 seen, but these would have strengthened, not weakened, the case 

 for the solar dichotomy. The solar cycle is one; its manifestations 

 in the two hemispheres, north and south, are different. 



