SUNSPOTS AND WEATHER. 5™ 



meteorological records, only those will be taken in which some possible 

 relation to the sunspot periods may exist. Thus a search is to be made 

 for 11-year periods to establish a good connection; the 35-year period 

 may furnish a possible connection between the two sets of phenomena, 

 although, as we have seen, its existence in the sunspot curves is too 

 doubtful to demonstrate the existence of the connection, while the 55- 

 to 65-year periods, even if they exist in the sunspot curves, are too 

 long to make a demonstration possible within the range of the recorded 

 meteorological observations. 



The best proof of the existence of an 11-year period has been 

 furnished by Koppen, who showed that there was such a cycle in the 

 combined mean annual temperature of many places within the tropics. 

 But the total range of variation is only about three-quarters of a 

 degree, while the mean annual temperatures show variations of from 

 five to ten degrees. This appears to be the only well-established quan- 

 titative result with respect to the 11-year period. But several 

 qualitative examinations have been made and the recent ones chiefly 

 refer to rainfall and famine in India. Sir Norman and Dr. W. J. S. 

 Lockyer have examined the rainfall statistics in India and Mauritius 

 and they come to the conclusion that India has an increased rainfall 

 near the sunspot maximum and Mauritius one near the sunspot mini- 

 mum, and further, that the latter gives rise to a smaller pulse of rain- 

 fall in India. Thus India has two periods of increased rainfall, a 

 large one near the sunspot maximum and a smaller one near the sun- 

 spot minimum. Unfortunately this investigation only refers to a 

 single period of eleven years — from 1877 to 1886. They have also 

 brought forward some evidence which indicates that the famine years 

 occur between these two pulses of rainfall. The results do not seem 

 to be sufficiently well made out to prophesy future famines with any 

 certainty. Last year another writer showed a connection between 

 certain Greenwich temperature records and the 11-year period, but 

 the differences shown were very small. Other investigations on the 

 same lines indicate about the same or a less degree of success in the 

 discovery of a sunspot period. 



In view of the doubtful existence of a 35-year period in the solar 

 activity it is unnecessary to say much concerning a similar period in 

 terrestrial phenomena. The most thorough investigation is that of 

 Bruckner, who examined a very large number of temperature records 

 from all parts of the earth and deduced from the annual means a 

 period of this length. But the amount of the change is only half a 

 degree Fahrenheit, while the annual averages differ amongst themselves 

 by from 5° to 10°. 



In summing up briefly the results of the evidence hitherto presented, 

 it must be admitted that no case has been made out in favor of a 



