26 



NA TURE 



\J\fay lo, 1877 



SUSPECTED RELATIONS BETWEEN THE 



SUN AND THE EARTH ^ 



II. 



IN my last article I endeavoured to show that as a 

 matter of fact there is an intimate connection between 

 the physical state of the sun's surface and tlic diurnal 



Planetary Influence on Si 



rant^e of the magnet freely suspended at the Kew Ob- 

 servatory. It was suggested that this relation might 



be that of cause and effect, inasmuch as the varia- 

 tions of spotted aica exhibited in ])iagram B invari- 



ably precede the 

 range. 



corresponding variations of magnetic 



' Contimied from p. 11, 



It cannot, however, with propriety be said that sun 

 spots are the cause of magnetic oscillations, for it has been 

 pointed out by Mr. J. A. Broun that even when there are no 

 spots on the solar surface the magnet hasyet a very consider- 

 able range in its daily oscillations. Then, on the other hand, 

 the spectroscopic rcsearchesof Mr. J.N. Lockyer and others 



leave us little room for doubting 



that there may Ije vast solar 

 activity without sun-spots, Avhile, 

 however, spots will probably 

 make their appearance when the 

 disturbance of the sun's surface 

 is very great. 



In fine, sun-spots will probably 

 only aflbrd us a rough means 

 of estimating solar activity just 

 as rainfall might give us a rough 

 means of estimating the meteoro- 

 logical activity of a district of 

 the earth. Is it not possible 

 that sun-spots are in truth a 

 species of celestial rainfall? 



Be this as it may, it is evident 

 that, inasmuch as sun-spots ex- 

 hibit a recurring period, wc are 

 entitled to say there is a period 

 of this kind in the meteorology 

 of the sun. The interesting ques- 

 tion then arises, What can be the 

 possible cause of such a period? 

 This question has been discussed by Mr. Warren De La 

 Rue and those associated with him in his solar researches. 

 The theory propounded by these 

 observers is that the planets are in 

 some unknown way concerned in the 

 production of spots. In their paper, 

 which will be found in the Proceedings 

 of the Royal Society for March, 1872, 

 they make the following remark : — 



"It might be said, 'How can a 

 comparatively small body like one of 

 the planets so far away from the sun 

 cause such enormous disturbances of 

 the sun's surface as we know sun-spots 

 to be ?' It ought, however, we think, 

 to be borne in mind that in sun-spots 

 we have, as a matter 0/ fact, a set of 

 phenomena curiously restricted to 

 certain solar latitudes, within which, 

 however, they vary according to some 

 complicated periodical law, and pre- 

 senting also periodical variations in 

 their frequency of a strangely complicated nature. Now 

 these phenomena must either be caused by something 

 within the sun's surface, or by some- 

 thing without it. But if we cannot 

 easily imagine bodies so distant as the 

 planets to produce such large effects, 

 we have equal difficulty in imagining 

 anything beneath the sun's surface 

 that could give rise to phenomena of 

 suchacomplicated periodicity. Never- 

 theless, as we have remarked, sun- 

 spots do exist, and obey complicated 

 laws, whether they be caused by 

 something within or something with- 

 out the sun. Under these circum- 

 cumstances, it does not appear to us 

 unphilosophical to see whether as a 

 matter of fact the behaviour of sun- 

 spots has any reference to planetary 

 positions. There likewise appears 

 to be this advantage in establishing a connection of 

 any kind i^between the behaviour of sun-spots and the 



