THE WEATHER AND THE SUN 487 



excess, not merely of light and beat, but of gravitating force, of mag- 

 netic influence, and of actinic or chemical action, exerted upon the 

 earth as a whole. Accordingly we find that there is a recognizable in- 

 crease in the activity of the earth's magnetism in December and Janu- 

 ary as compared with June and July. But, assuredly the effect pro- 

 duced is not of such a character as to suggest that we should find the 

 means of predicting weather, if it were possible for us now to discover 

 any solar law of change resulting in a corresponding variation of solar 

 action upon the earth. 



This leads us to consider the first great law of solar change as dis- 

 tinguished from systematic variations like the sun's varying change 

 of distance and his varying daily path on the heavens. This law is 

 that which regulates the increase and decrease of the solar spots with- 

 in a period of about eleven years. The sun's condition does not, in- 

 deed, admit of being certainly predicted by this law, since it not un- 

 frequeutly happens that the sun shows few spots for several weeks 

 together, in the very height of the time of spot-frequency, while on 

 the other hand it often happens that many and large spots are seen at 

 other times. Nevertheless, this general law holds, that, on the whole, 

 and taking one month with another, there is a variation in spot-fre- 

 quency, having for its period an interval of rather more than eleven 

 years. 



Now, the difference between a year of maximum spot-frequency 

 and one of minimum frequency is very noteworthy, notwithstanding 

 the exceptional features just mentioned, which show themselves but 

 for short periods. This will be manifest on the consideration of a few 

 typical instances. Thus, in the year 1837, the sun was observed on 

 168 days, during which he was not once seen without spots, while no 

 less than 333 new groups made their appearance. This was a year of 

 maximum spot-frequency. In 1843, the sun was observed on 312 days, 

 and on no less than 149 of these no spots could be seen, while only 34 

 new groups made their appearance. This was a year of minimum spot- 

 frequency. Passing to the next maximum year, we find that in 1848 

 the sun was observed on 278 days, during which he was never seen 

 without spots, while 330 new spots made their appearance. In 1855 

 and 1856 together, he was observed on 634 days, on 239 of which he 

 was without spots, while only 62 new groups made their appearance. 

 The next maximum was not so marked as usual, that is, there was not 

 so definite a summit, if one may so speak, to the wave of increase ; but 

 the excess of spot-frequency was none the less decided. Thus, in the 

 four years, 1858-'61, the sun was observed on 335, 343, 333, and 322 

 days, on not one of which he was spotless, while the numbers of new 

 groups for these four years wei-e, respectively, 202, 205, 211, and 204. 

 The minimum in 1867 was very marked, as 195 days out of 312 were 

 without spots, and only 25 new groups appeared. The increase after 

 1867 was unusually rapid, since in 1869 there were no spotless days, 



