REACTION OF PLANETS UPON SUN PUISEUX. 169 



CHECK METHODS. 



This result is in a way too beautiful. We had hoped to find only 

 a small influence and we find one so decided that there is little room 

 left for the other planets. Accordingly, search has been justly made 

 for other proofs. We may, for instance, compare — 



(1) Only the areas, in the east and west halves, of the groups of 

 long life which have been completely followed across the disk. Here, 

 again, without exception, for all symmetrical pairs of zones, the ad- 

 vantage remains with the eastern half of the disk. 



(2) We may retain only the groups of long life seen in more than 

 two successive rotations, neglecting the first and last appearances, 

 keeping only the intermediate appearances. It is evident that in 

 this way no appearance can be omitted or fictitious disappearance be 

 registered. Despite these safeguards, the eastern portion still re- 

 tains its advantage in the proportion of 19 parts in 100. 



(3) We may substitute for the spot statistics those obtained from 

 the protuberances observed on the east and west limbs and see if 

 the protuberances show the same inequalities in activity as do the 

 spots at the limb zones. 



The protuberances, we have seen, follow more or less closely the 

 solar cycle in their development. But the method of observation for 

 the protuberances is quite difi'erent than for the spots. Mrs. Maunder 

 found no sufficiently complete and homogeneous series of observations 

 of the protuberances for the interval 1889 to 1901, which her spot 

 statistics covered. The studies of Eicco at Catania, however, cover 

 well the interval between the last two spot maxima. Diagrams made 

 from this data show that from 1892 to 1900, during the decrease in 

 spot numbers, the eastern limb had on the average more protuber- 

 ances than the western limb. The opposite condition held from 1900 

 to 1904, but after the spot maximum was reached in 1905 the eastern 

 limb again regained its ascendancy. On the average, the eastern 

 limb maintained a superiority of 1 to 20, less constant and less marked 

 than in the case of the spots, but in the same sense. 



Deslandres has recently pointed out a circumstance which may ren- 

 der the protuberances more easily visible on the east than on the 

 west border. The sun, which we have reason to believe is electrified 

 at its surface, must by its rotation create a magnetic field. The very 

 mobile protuberances would be disturbed by this field so as to be 

 bent at their upper part in the direction of the rotation. An observer 

 would then not be in an impartial position relative to the two limbs 

 of the sun. He will see better the oncoming protuberances which 

 would be bent toward him than the disappearing ones which would 

 be bent away. This hypothesis seems to be confirmed by the deforma- 

 tions and velocities of the protuberances. 



