118 



Prof. B, Stewart on the Daily 



[Mar. 22, 



In Figs. VIL and VIII. the supposed inequalities due to the above period 

 are compared together for solar spotted area and declination-range. It 

 will be noticed that the latter lags visibly behind the former in point of 

 time. 



P. MemarJcs on the supposed relations between Solar spotted areas, 

 Declination-ranges, and Temperature-ranges. 



15. A few remarks on this subject will not be considered unallowable 

 if the object be not so much to introduce a final theory as to suggest a 

 working hypothesis which, while not inconsistent with any well-esta- 

 blished fact, may perhaps serve to direct future inquiry. 



In the first place, we may conclude, as the result of the comparison of 

 Pigs. I. and II., that the connexion between spotted areas and declination- 

 ranges is of an intimate nature, the smaller inequalities of the one being 

 reproduced in the other with modifications. 



16. In the next place, it seems almost certain that sun-spots are not 

 the chief cause of magnetic action. Mr. Broun, in a recent paper " On 

 the Decennial Period in the Eange and Disturbance of the Diurnal Oscil- 

 lations of the Magnetic Needle and in Sun-spot area" (Trans. Roy. 

 Soc. Edinb. 1876), has made a remark similar to the above, founding it upon 

 the fact that sun-spots appear only when the magnetic action exceeds a 

 given value. 



17. Nevertheless it is most probable that magnetic activity is some- 

 how caused by the sun, depending perhaps on the physical state of his 

 surface, while sun-spots give us only a rough mode of estimating this 

 physical state, just as rainfall might in estimating the climate of a place. 

 For it will be seen that the effect of the sun upon magnetic range bears 

 all the appearances of being due to an influence emanating from our 

 luminary. Por just as the maxima of yearly and daily temperature lag 

 behind the corresponding maxima of solar heat influence, so do the maxima 

 and minima of declination- range lag behind the corresponding maxima 

 and minima in the solar curve, while the same lagging behind appears in 

 the curves, denoting the supposed influence of the planets on the state of 

 the solar surface and (through it ?) on the magnetic range. 



18. Again, we may probably imagine that sun-spots give us a roughly 

 true indication of solar activity ; for if this were not so it would be 

 difficult to account for the striking likeness between the sun-spot plane- 

 tary curves and the declination-range planetary curves. That the sun- 

 spots afford but a rough indication of the physical state of the sun will of 

 course be gathered from the fact that the sun is influential both in meteo- 

 rology and magnetism when there are no spots ; and the same conclusion 

 appears to be supported by the fact that the planetary inequalities appear 

 to be more pronounced when derived from declination-ranges than when 

 derived from sun-spots. 



19. There seems, however, to be something more than this ; there 



