An Introduction to the Study of South African Rainfall. 21 



u z . u' x . 



Section IX. W -402 824 



VIII. W. ... -417 561 



VI. W -151 135 



V. W 191 210 



IV. W -147 86 



The following is the variation from east to west in the absolute 

 amplitude of the second harmonic term : — 



Section XV. .. 



n 2 . 



. -112 



Section XII 



u 2 . 



•182 



Section X 



»2, 



•322 



XIII... 



•370 



XI 



•404 



VII. ... 



•245 



XIV... 



•347 



VIII. E... 



•264 



VI. E. . 



•134 



IX. E. . 



•241 



VIII. W.. 



•157 



VI. W.. 



•218 



IX. W. 



•199 



Ill 



•112 



II. ... 



•281 



III. .. 



•112 







I 



•562 



A remarkable feature about these amplitudes is that they tend to 

 a maximum from the tableland side of the Drakensbergen southward 

 to the sea. Thus the region of spring and autumn rains penetrates 

 from the South Coast and Southern Karroo at least as far as the 

 mountains of Basutoland. The reason why it cannot be easily 

 ■detected in the monthly averages of Table 25 is that it is swallowed 

 up by the great relative amplitude of the first term. 



The corresponding values, in relative measure, are — 



u' 2 . u' 2 . u' 2 . 



Section XV. ... 38 Section XII. 82 Section X 134 



XIII... . 132 XI 207 VII.... 192 



XIV.... 179 VIII. E. 206 VI. E. 171 



IX. E. 191 VIII. W. 211 VI. W. 195 



IX. W. 408 III 140 II 149 



III. ... 140 1 167 



We are better able now to understand how it comes about that 

 while nearly the whole of Sections IV. and V. have maxima of rain- 

 fall in autumn and spring, the western halves of both have the 

 primary maximum in April or May, whereas the eastern stations 

 have either a primary maximum or a greatly increased (relatively) 

 secondary maximum in September. At first sight we should expect 

 that the maxima of these eastern stations would approximate to 

 those of the neighbouring Sections VII., VIII. E., and XL, rather 

 than that the western stations should do so. But the explanation, 



