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METEOROLOGY 95 



ject. Weather reports every three hours would be desirable, but 

 since the development of aviation at present does not warrant this, 

 a system of telegraph and wireless communication between mete- 

 orological stations has been evolved to provide individually for 

 each flight. For non-scheduled flights the arrangements are not 

 yet satisfactory. Since flights usually begin at an early hour, the 

 issue of weather reports from all stations soon after dawn is being 

 urged. It should be remembered that African circumstances are 

 very different from those of Europe, where numerous aeroplanes 

 are always in transit. 



Data on rainfall are more complete for the Union than for any 

 other part of the continent, with the possible exception of Egypt. 

 Rainfall is now recorded at 4,074 stations, including the seventeen 

 in Bechuanaland, thirty in Swaziland, and thirty-one in Basuto- 

 land. The official publications on this subject are the annual 

 reports of the Meteorological Office and chapters in the annual 

 handbook; A, D. Lewis (1927), of the Meteorological Office, has 

 analysed all rainfall normals up to the end of 1925. Much material 

 has also been published by the universities and in scientific journals, 

 and reference is made in the bibliography to important papers by 

 J. M. Sim (191 7), F. E. Plummer (1926 and 1932), Professor of 

 Geography at Pretoria, J. R. Sutton (1921), Schumann and 

 Thompson (1934) on rainfall; Howard (1920), Spencer (1926), 

 Evelyn (1904), and Schumann (1936) on general climatology; 

 Schonland and Craib (1927) on the electric fields of thunder- 

 storms. In addition to the Meteorological Office and the Universi- 

 ties, the Union Observatory at Johannesburg is a centre of research, 

 and the Director, Mr. Wood, has contributed much to meteorology 

 in South Africa. 



A general analysis of the available data has been made by Plum- 

 mer and Leppan (1927), who point out the practical importance of 

 even minute local variations in determining the competitive advan- 

 tages of different agricultural areas. Professor Plummer is aiming 

 at procuring accurate standard normals of rainfall over the whole 

 country. It should be noted, however, that stable averages of rain- 

 fall, or any element of weather, do not exist in any part of the 

 world. Approximations to averages on a fifty-year period are as 

 much as can profitably be sought. 



