Solar Changes of Temperature and Variations in 7<V ////"//. 423 



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

 nected with the south-east trade in the Indian Ocean. 



The rainfall of Cordoba suggests that the same trade wind in the 

 Atlantic Ocean was similarly affected at the same time. 



The Cause of the - Pulse. 



Mr. Eliot long ago conjectured that the rainfall of India was pro- 

 foundly modified by events taking place from time to time in the 

 Southern Ocean. In his " Annual Summary " for 1896 he wrote us 

 follows : 



" It has apparently been established in the discussion that the varia- 

 tions of the rainfall in India during the past six years are parallel 

 with, and in part, at least, due to variations in the gradients, and the 

 strength of the winds in the south-east trade regions of the Indian 

 Ocean. The discussion has indicated that there are variations from 

 year to year in the strength of the atmospheric circulation obtaining 

 over the large area of Southern Asia and the Indian Ocean, and that 

 these variations are an important and large factor in determining the 

 periodic variations in the rainfall of the whole area dependent on that 

 circulation, and more especially in India. It has also been indicated 

 that these variations which accompany, and are probably the result in 

 part of abnormal temperature (and hence pressure) conditions in the 

 Indian Ocean and Indian monsoon area, may be in part due to condi- 

 tions in the Antarctic Ocean, which also determine the comparative 

 prevalence or absence of icebergs in the northern portions of the 

 Antarctic Ocean." 



We have begun an investigation into the pressure changes which 

 have been recorded in this region, but it will be some time before it is 

 finished. The idea underlying the inquiry is that the reduced solar 

 temperature may modify the pressure so that the high pressure belts- 

 south of Mauritius may be broken up and thus allow cyclonic winds 

 from a higher latitude to increase the summer rains, as they certainly 

 were increased at the normal minima of 1877 and 1888. 



It has been shown that the - pulse is felt in India about a year 

 later than it commences action in the Southern Ocean ; while in some 

 cases the + pulse is felt almost simultaneously in India and at the 

 southern stations. 



Tiie Rainfall at tlie Cape, Batavia, and Cordoba, fw the period 



18771886. 



Each of the curves (fig. 1) illustrating the rainfall for the Cape and 

 Cordoba (Arg.) for this period shows two prominent maxima in the 

 years 1878 and 1883 ; these correspond nearly with the + and - pulses 



