488 THE POPULAR SCIENCE MONTHLY. 



and 224 new groups were seen, though the sun was only observed on 

 196 days. The number of spots in 1870, 1871, and 1872, as well as 

 their magnitude and duration, has been above what is usual, even at 

 the period of maximum spot-frequency. 



From all this it will be manifest that we have a well-marked pecu- 

 liarity to deal with, though not one of perfect uniformity. Next to 

 the systematic changes already considered, this alternate waxing and 

 waning of spot-frequency might be expected to be efficient in produ- 

 cing recognizable weather-changes. Assuredly, if this should not 

 appear to be the case, we should have to dismiss all idea that the sun- 

 spots are weather-rulers. 



Now, from the first discovery of spots, it was recognized that they 

 must, in all probability, affect our weather to some degree. It was 

 noticed, indeed, that our auroras seemed to be in some way influenced 

 by the condition of the sun's surface, since they were observed to be 

 more numerous when there are many spots than when there are few or 

 none. Singularly enough, the effect of the spots on temperature was 

 not only inquired into much later (for we owe to Cassini and Mairan 

 the observation relating to auroras), but was expected to be of an op- 

 posite character from that which is in reality produced. Sir W. Her- 

 schel formed the opinion that, when there are most spots, the sun 

 gives out most heat, notwithstanding the diminution of light where 

 the spots-are. He sought for evidence on this point in the price of 

 corn in England, and it actually appeared, though by a mere coinci- 

 dence, that corn had been cheapest in years of spot-frequency, a re- 

 sult regarded by Herschel as implying that the weather had been 

 warmer on the whole in those years. It was well pointed out, how- 

 ever, by Arago, that " in these matters we must be careful how we 

 generalize facts before we have a very considerable number of obser- 

 vations at our disposal." The peculiarities of weather in a single and 

 not extensive country like England are quite insufficient to supply an 

 answer to the wide question dealt with by Herschel. The weather 

 statistics of many countries must be considered and compared. More- 

 over, very long periods of time must be dealt with. 1 



1 When Herschel made his researches into this subject, the law of spot-frequency had 

 not been discovered. He would probably have found in this law, as some have since 

 done, the explanation of the seven years of plenty and the seven years of famine, typified 

 by the fat kine and lean kine of Joseph's dream. For, if there were a period of eleven 

 years in which corn and other produce of the ground waxed and waned in productive- 

 ness, it would be not at all unlikely that, when ever this waxing and waning chanced to be 

 unusually marked, there would result two series of poor and rich years apparently rang- 

 ing over fourteen instead of eleven years. We have seen, above, that the waves of spot- 

 waxing and spot-waning are not all alike in shape and extent. Whenever, then, a wave 

 more marked than usual came, we should expect to find it borrowing, so to speak, both 

 in trough and crest, from the waves on either side. It would require but a year or so 

 either way to make the wave range over foui'teen years ; and observed facts, even during 

 the last half-century only, show this to be no unlikely event. 



