CLIMATIC REQUIREMENTS 3 i 



conditions. The term " cool " is relative, and may be mis- 

 leading, for in those parts of the Transvaal where the maize 

 crop thrives the summer nights are invariably cool. The 

 director of the Union Observatory gives the following figures 

 showing the mean daily temperature at 6 a.m. (the coolest 

 hour of the night) at the Government Observatory, Johannes- 

 burg. 



CHAP. 



n. 



Table IV. 1 



MEAN MINIMUM TEMPERATURES AT GOVERNMENT 

 OBSERVATORY, JOHANNESBURG. 



September, 1904 — March, 1909. 



At Buenos Aires the mean minimum summer temperature (December to 

 February) at 5 a.m. is 63-5° Fahr. 



1 Abstracted from Reports of Transvaal Department of Meteorology 

 (I lines, 1). 



2 N.B. — The mean daily minimum is 17 lower than the mean tempera- 

 ture at 6 a.m. 



The following tables, taken from the publications of the 

 late Transvaal Department of Meteorology, Johannesburg 

 ijnnes, i) show the mean daily minimum temperature over a 

 series of years at Vereeniging (4,700 feet altitude), and Bethal 

 (5,580 feet altitude), two of the most important maize centres 

 of the Transvaal. Comparing the two tables we find that for 

 the 880 feet difference in altitude we have an average differ- 

 ence in the annual mean of 1 '2°, and in the 7 months' mean 

 of 27 . 



