December 6, 1 900] 



NATURE 



129 



The variations in the intensities of the pulses of rain at 

 the successive maxima and minima are very remarkable, 

 and suggest the working of a higher law, of which we have 

 other evidence. But, putting this aside for the present, it 

 should be pointed out that even normally we should not 

 expect the same values for the rainfalls in 1882 and 1893, 

 because the amount of spotted area was so different, 1 160- 

 millionths of the solar surface being covered with spots 

 in 1883, and 1430 in 1893. 



The very considerable variation in the quantity of 

 snowfall on the Himalayas has often been pointed out 

 by the Indian meteorologists. We have, therefore, used 

 the "whole India" curve between 1875 and 1896, to see 

 whether the sun pulses, which we have found to be bound 

 up with the Indian rainfall, are in any way related to the 

 snowfall as might be expected. 



The Himalayan snowfall beyond all question ^ fol- 

 lows the same law as the rain, the values occurring at 

 the + and - pulses, as under, being among the 

 highest : — ^ 



inches 

 - 1867-8 ... 134 



— + 187I-2 

 1877-8 



- + 1882-3 



207 



From these tables it follows that both in rainfall and 

 snow the quantity is increased in the years of the rise 

 both of the unknown and iron lines. 



Other Rainfalls. 



Being in presence of pulses of rainfall in India during 

 the south-west monsoon, corresponding with pulses of 

 solar change, it became necessary to attempt to study 

 their origins. We may add that other pulses were traced, 

 especially one in 1875, but the simplest problem was 

 considered alone in the first instance. 



The rainfalls at the Mauritius, Cape Town and Batavia 

 were collated to see if the pulses felt in India were 

 traceable in other regions surrounding the Indian Ocean 

 to the south and east. 



The Mauritius Rainfall. 



The rainfall of Mauritius has been obtained by utilis- 

 ing the results that have been published in the Blue 

 Books 2 issued by the Royal Alfred Observatory since 

 the year 1885. The volume for 1886 gives the yearly 

 total rainfall for every station that was then in use from 

 1861 up to the year 1885, and these values have been 

 employed ; since then the yearly values have been ob- 

 tained direct from each of the yearly volumes subsequently 

 published, i.e. to the end of the year 1898. 



It was at first thought that the total Mauritius rainfall 

 could be fairly obtained by employing for the period 

 between 1861 and 1886 the means of several stations as 

 given by Meldrum,^ and continuing the values from the 

 observations published in the more recent yearly 

 volumes. 



It was found, however, that from 1861-1880 the rain- 

 fall was obtained from the observations of four stations, 

 while from 1 871- 1886 the observations from eight stations 

 were employed. 



As a study of all the published data showed that more 

 stations might be utilised in determining the total rainfall 

 of Mauritius, it was decided to discuss all the observa- 

 tions afresh, and make use of as many as possible. 



To this end the records of twenty-eight stations, 



1 I.M.M., vol. iii. p. 235. 



2 " Mauritius Meteorological Results." 



3 1861-1880. Relations of Weather to Mortality, &c., 1881, p. 36. 

 1871-1886. Annual Repoit of the Director of the Royal Alfred Observa- 

 tory for 1886, p. 18. 



situated in six different districts, were chosen, and the 

 total rainfall for each year obtained. It is only natural 

 that the number of rain-gauge stations in the early 

 year of i860 was not so numerous as that of more 

 recent years ; the facts may be stated as follows : — 



With regard to the general rainfall of Mauritius 

 throughout the year, it may be stated that on the average 

 the most rainy months are from December to April, both 

 months inclusive. 



The months of November and May are those in which 

 the daily rainfall is increasing and diminishing respec- 

 tively. Sometimes in July or August there is a slight 

 tendency for a small increase. 

 The Mauritius Rainfall Curve for the period 1877- 1886. 



In plotting the Mauritius rainfall curve for the period 

 1 877- 1 886, it was observed that the curve is of a fairly 

 regular nature, showing alternately an excess and 

 deficiency of rainfall. 



The highest and lowest points of the curve will be 

 gathered from the following table : — 



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 about 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. 



Comparison of the Mauritius Rainfall with those of Leh, 

 Murree and Newera Eliyafor the period 1 877-1886. 

 The most prominent feature of the Mauritius rainfall 



for this period was the great excess in the years 1877 and 



1882. 



NO. 1623, VOL. 63] 



