THE WEATHER AND THE SUN. 49 i 



has been strongly marked, and might be viewed as demonstrated 

 only it chances, unfortunately, that, for two other cases, the relation is 

 precisely reversed ; and, in point of fact, whereas the period now as- 

 signed to the great sun-spot wave is eleven years and rather less than 

 one month, Jupiter's period of revolution is eleven years and about ten 

 months, a discrepancy of nine months, which would amount to five 

 and a half years (or modify perfect agreement into perfect disagree- 

 ment) in seven or eight cycles. 



But, accepting the association between weather and the sun-spot 

 changes as demonstrated (which is granting a great deal to the be- 

 lievers in solar weather-prediction), have we any reason to believe that 

 by a long-continued study of the sun the great problem of foretelling 

 the weather can be solved ? This question, as I have already pointed 

 out, must not be hastily answered. It is one of national, nay, of cos- 

 mopolitan importance. If answered in the affirmative, there is scarce- 

 ly any expense which would be too great for the work suggested ; but 

 all the more careful must we be not to answer it in the affirmative, if 

 the true answer should be negative. 



But it appears to me that so soon as the considerations dealt with 

 above have been fairly taken into account, there can be no possible 

 doubt or difficulty in replying to the question. The matter has, in 

 effect, though not in intention, been tested experimentally, and the 

 experiments, when carried out under the most favorable conditions, 

 have altogether failed. To show that this is so, I take the position 

 of affairs before Schwabe began that fine series of observations which 

 ended in the discovery of the great spot-period of eleven years. Let 

 us suppose that at that time the question had been mooted whether 

 it might not be possible, by a careful study of the sun, to obtain some 

 means of predicting the weather. The argument would then have run 

 as follows : " The sun is the great source of light and heat ; that orb 

 is liable to changes which must in all probability affect the supply of 

 light and heat ; those changes may be periodical, and so predictable ; 

 and, as our weather must to some extent depend on the supply of light 

 and heat, we may thus find a means of predicting weather-changes." 

 The inquiry might then have been undertaken, and undoubtedly the 

 great spot-period would have been detected, and with this discovery 

 would have come that partial power of predicting the sun's condition 

 which we now possess that is, the power of saying that in such and 

 such a year, taken as a whole, spots will be numerous or the reverse. 

 Moreover, meteorological observations conducted simultaneously would 

 have shown that, as the original argument supposed, the quantity of 

 heat supplied by the sun varies to a slight degree with the varying 

 condition of the sun. Corresponding magnetic changes would be de- 

 tected ; and also those partial indications of a connection between 

 phenomena of wind and rain and the sun's condition "Nvhich have been 

 indicated above. All this would be exceedingly interesting to men of 



