1876.] Rainfall in connexion with Sun-spots. 385 



belonging to different zones. The positions of the belts of calms and 

 variables may be found to have a secular variation. 



It is to be borne in mind that the average excess of rainfall in the 

 maxima years (6* 19 inches) is obtained by taking all the observations 

 of whatever description. Most of the observations are favourable, but 

 others are unfavourable. If the former alone had been taken, the excess 

 would be much larger. JNTow the rainfall at many of the stations seems 

 to be permanently favourable, while at several others it seems to be per- 

 manently unfavourable*; that is, there are many stations at which the 

 rainfall is invariably, or at least generally, greater in the maxima than 

 in the minima years, while at some others the reverse takes place. As 

 a rule, it would appear that the stations near the sea and fully exposed 

 to winds sweeping over a considerable expanse of water are favourable, 

 while the unfavourable ones are those exposed to winds passing over 

 land and liable to be deflected by mountains and valleys. Bombay, 

 Madras, Mauritius, Cape of Good Hope, Brisbane, Melbourne, Plymouth, 

 and Charleston (U.S.) are among the favourable stations, and Calcutta, 

 Milan, and Trieste amongst the unfavourable. At Bombay (exposed to 

 the S. W. monsoon) there has been only one exception to the general 

 law since 1817, and at the Cape of Good Hope, Mauritius, &c, as far as 

 observation extends, there has been no exception at all. On the other 

 hand, Milan furnishes an opposite example. What we have to do, then, 

 is to separate the favourable from the unfavourable stations, and to study 

 the rainfall of each class by itself. The total rainfall of the globe 

 generally is about 6 inches greater in the maxima than in the minima 

 sun-spot years; but there are local exceptions, and it is important to 

 know their laws. 



As the rainfall at a majority of stations fluctuates with the sun- 

 spots, and as the amount of fluctuation for these stations is considerably 

 greater than 6 inches, it would probably be of advantage to be able to 

 predict the epochs of maximum and minimum sun-spots. Dr. De La 

 Hue and Prof. Balfour Stewart have shown that the sun-spots are, to 

 some extent, connected with the relative positions of the planets and 

 sun. If, then, it were proved that the sun-spot period depends upon 

 the configuration of the planets, and the rainfall period on sun-spots, it 

 would be easy to predict the general character of the seasons for large 

 portions of the globe. Even without this it is possible, as recently 

 pointed out by Mr. Ellery, in his Annual Address to the Royal Society 

 of Victoria, that there is so much interdependence in the rainfalls 

 of different countries, that, with our present knowledge and with the 

 aid of the telegraph, we may shortly be in a position to foretell whether 

 a coming season is likely to be a wet or a dry one. The results of the 



* These are few in number. Observations for long periods show that the law of 

 fluctuation holds good at a great majority of stations. 



