466 POPULAR SCIENCE MONTHLY 



sun, but as the instigators of the terrestrial variations.' These investi- 

 gations, however interesting and important they may be to astronomers 

 and physical meteorologists, are really outside the field of climatology. 



In 1872 Meldrum, then director of the meteorological observatory 

 at Mauritius, first called attention to a sunspot periodicity in rainfall 

 and in the frequency of tropical cyclones in the South Indian Ocean. 

 Tbe latter are most numerous in years of sunspot maxima, and decrease 

 in frequency with the approach of sunspot minima. Poey later found 

 a similar relation in the case of the West Indian hurricanes. Mel- 

 drum's conclusions regarding rainfall were that, with few exceptions, 

 there is more rain in years of sunspot maxima. This is to be taken 

 only for means, and for a majority of stations, and is not to be expected 

 at all stations or in every period. Hill found it to be true of the 

 Indian summer monsoon rains that there seems to be an excess in the 

 first half of the cycle, after the sunspot maximum. The winter rains 

 of northern India, however, show the opposite relation; the minimum 

 following, or coinciding with, the sunspot maximum. Many studies 

 have been made of a possible relation between rainfall and the sunspot 

 period, but the conclusions are not very definite, are sometimes con- 

 tradictory, and do not yet warrant any general practical application 

 for purposes of forecasting the wet or dry character of a coming year. 

 Particular attention has been paid to the sunspot cycle of rainfall in 

 India, because of the close relation between famines and the summer 

 monsoon rainfall in that country. In 1889 Blanford admitted that 

 the rainfall of India as a whole did not give evidence of the sunspot 

 cycle in the records of the twenty-two years preceding. More recently 

 the Lockyers have studied the variations of rainfall in the region sur- 

 rounding the Indian Ocean in the light of solar changes in temperature. 

 They find that India has two pulses of rainfall, one near the maximum 

 and the other near the minimum of the sunspot period. The famines 

 of the last fifty years have occurred in the intervals between these two 

 pulses, and these writers believe that if as much had been known in 

 1836 as is now known, the probability of famines at all the subsequent 

 dates might have been foreseen. 



Belations between the sunspot period and various meteorological 

 phenomena other than temperature, rainfall and tropical cyclones have 

 been made the subject of numerous investigations, but on the Avhole the 

 results are still too uncertain to be of any but a theoretical value. Some 

 promising conclusions seem, however, to have been reached in regard 

 to pressure variations, and their control over other climatic elements. 



Bruckner's Thirty- five-year Cycle. — Of more importance than the re- 

 sults thus far reached for the sunspot period are those which clearly estab- 

 lish a somewhat longer period of slight fluctuations or oscillations of cli- 



