THE SPOTS ON THE SUN. 155 



leaves ' the ' things ' on the sun to be the tops of the currents 

 ascending from the sun's body, what changes of appearance are the} 

 likely to undergo in the neighborhood of a cyclone ? For some dis- 

 tance round a cyclone there will be a drawing-in of the superficial 

 gases toward the vortex. All the luminous spaces of more transparent 

 clouds, forming the adjacent photosphere, will be changed in shape by 

 these centripetal currents ; they will be greatly elongated, and those 

 peculiar aspects which the penumbra presents will so be produced." 



Mr. Spencer, however, in his article in the former number of The 

 Popular Science Monthly, says that at present none of the inter- 

 pretations of the solar spots can be regarded as established. 



" All this is, no doubt, very curious, but it is very remote and un- 

 practical. What have the solar spots to do with me, or I with the 

 solar spots ? " exclaims some impatient reader. But suppose it turns 

 out that the spots on the sun do have a very close connection with 

 earthly affairs what then? The story of these strange appearances is 

 incomplete till this point also is noticed. 



The view which connects the spots with cyclonic action is con- 

 firmed by the now demonstrated fact that they are mighty solar agita- 

 tions, whose influence is felt in distant planets. Schwabe has discov- 

 ered that the spots, instead of being uniform in number and intensity 

 from year to year, have a periodicity increasing to a maximum, and then 

 declining to a minimum in a course of years. The variations consisted 

 in the number of days in the year in which spots were visible, and in 

 the number of groups observed. The indomitable perseverance of this 

 astronomer is something wonderful. The president of the English As- 

 tronomical Society, in awarding him its gold medal, said: " For thirty 

 years, never has the sun exhibited his disk above the horizon of Dessau, 

 without being confronted by Schwabe's imperturbable telescope, and 

 that appears to have happened about 300 days in a yeai\ So that, 

 supposing he observed but once a day, he has made 9,000 observations, 

 in the course of which he has discovered 4,700 groups." In these 

 observations, he traced three complete oscillations from maximum 

 frequency, through minimum back to maximum again. The period 

 assigned by Schwabe was about ten years, although Prof. Wolf, of 

 Zurich, has showed that 11.11 years (or the ninth part of a century) 

 is indicated rather than a ten-yearly period. 



It has been established that there is a coincidence between this 

 sun-spot period and magnetic disturbances on the earth. In every 

 part of the earth the magnetic needle has at any given time a certain 

 definite position, about which, under normal conditions, it will oscillate 

 during the day. Proctor says : 



"Each day the needle oscillates gently about its position of rest, the oscil- 

 lation corresponding to a very slight tendency, on the part of that end of the 

 needle which lies nearest to the sun, to direct itself toward his place. The daily 

 oscillation is itself variable in a systematic manner, not only with the progress 



