440 Transactions of the South African Philosophical Society. 



observations made at the Durban Botanical Gardens from 

 1873-1883 and at the Government Observatory from 1884-1904. 

 It has not been possible to form tables of monthly departures from 

 average rainfall for the whole of Natal. Such tables are, however, 

 very desirable, as the rainfall at Durban, particularly in the winter 

 months, is erratic. Frequently a very dry month will show a 

 rainfall much in excess of normal owing to floods on one or two days. 



The information for Mauritius is based upon the returns from 

 ten representative stations in different parts of the island, and may be 

 considered as an accurate numerical statement of the droughts 

 which have occurred. 



From the preceding table it will be seen that winter droughts at 

 Durban have invariably been followed by summer droughts in 

 Mauritius at intervals of from three to seven months, and that 

 prolonged droughts at Natal, or those commencing in the summer, 

 may be either accompanied or followed by prolonged droughts 

 in Mauritius. 



With a view to ascertaining whether the interval is dependent 

 upon the date of commencement, duration, or intensity at Durban 

 the droughts have been grouped in the following table according to 

 the interval between the commencement of the drought at Durban 

 and in Mauritius. 



There is some evidence to show that the interval depends upon 

 the time of commencement of the drought at Durban, the former 

 varying inversely with the latter, in the mean ; but the interval, 

 duration, and intensity of the Mauritius droughts appear to be 

 independent of the duration or intensity of the Natal droughts, 

 at least so far as winter droughts are concerned. 



There is this connection, however, that whereas winter droughts 

 at Durban are followed by summer droughts in Mauritius, prolonged 

 droughts at Durban lasting over summer and winter, or longer, are 

 either accompanied, or followed, by prolonged droughts in Mauritius. 



The first prolonged drought at Durban, which commenced in 

 February, 1876, and lasted practically up to December, 1878, was 

 accompanied by a prolonged drought in Mauritius from March, 

 1876, to December, and followed by a second very severe drought in 

 Mauritius from October, 1879, to March, 1881. 



The second prolonged drought at Durban, from February, 1885, to 

 January, 1886, was accompanied and followed by a prolonged 

 drought in Mauritius from November, 1885, to December, 1886. 



The third prolonged drought at Durban, from May, 1895, to June, 

 1896, was followed by a prolonged drought in Mauritius from June, 

 1896, to May, 1897. 



