180 SOLAR CHANGES OF TEMPERATUKE. 



The months of November and May are those in Avhich the daily 

 rainfall is increasing and diminishino-, respectively. Sometimes in 

 July or August there is a slight tendcnc}^ for a small increase. 



THE MAUKITIUS RAINFALL CURVES FOR THE PERIOD 1877-188(5. 



In plotting the Mauritius rainfall curve for the period 1877-1886, it 

 was observed that the curve is of a fairly regular nature, showing 

 alternately an excess and deficiency of rainfall. * * * 



Comparing the times of occurrence of the two pulses of rainfall at 

 Mauritius with the times of the crossings of the known and unknown 

 lines, it is found that the Mauritius maximum rainfall of 1877 occurs 

 a])out a year after the rise of the known lines in 1876. The next 

 Mauritius pulse of rainfall in 1882 follows the succeeding crossing, 

 when the unknown lines are going up, also about a year later. * * * 



The delay of about a yenv in the effect of the Mauritius pulse being 

 felt in Ceylon and India is exactly what would be expected if the rain 

 at sun-spot minimum comes from the south, as has been surmised. 



The fact that the pulses at Mauritius, Ceylon, and India in 1882 

 occur simultaneously is very strong eA^idence in favor of an origin in 

 the equatorial region itself for the Indian rain at sun-spot maximum. 

 The pulse at maximum in the Indian southwest monsoon may depend 

 to a large extent upon the action of the excess of solar heat on the 

 equatorial waters to the south of India, and not on an abnormal effect 

 on the southeast trade. * * * 



RESULT OF THE COMPARISON OF RAINFALL. 



It seems quite certain that we are justified in associating the 1878 

 pulse of rainfall during the southwest monsoon in India with the rain- 

 fall common to Mauritius, Batavia, and the Cape at that date; that in 

 all cases the rain has been associated with some special condition con- 

 nected with the southeast trade in the Indian Ocean. 



The rainfall of Cordova suggests that the same trade Avind in the 

 Atlantic Ocean was similarly affected at the same time. * "' * 



SUBSIDIARY PULSES. 



In a normal sun-spot curve we find a sharp rise, generall}' taking 

 three or three and a half j^ears, to maximum, and a slow decline to 

 minimum, on which the remaining years of the cycle are spent. 



The curve on the upward side rises generally regularly and continu- 

 ousl}^; on the downward portion the regularity of the curve is very 

 often broken by a "hump" or sudden change of curvature. There 

 has not yet been a complete discussion of the number and character of 

 the prominences associated with the spots during the cycle; Ave have 

 found, however, that the ''hump" in the sun-spot curA^e in 1871 was 

 accompanied by a rcnnarkable increase in the number of eruptive 

 prominences. * * * 



