Rainfall and the Pressure Gradient. 
63 
have a limited use in long-range forecasting. It is to be hoped that the 
investigation may be carried further, seeing that it promises a certain 
measure of information beyond the mere requirements of weather prediction. 
As Lord Rayleigh, thirty years ago, truly said, " In order to introduce 
greater precision into our ideas respecting the behaviour of the earth's 
atmosphere, it seems advisable to solve any problems that may present 
themselves." 
Table I. — Monthly mean Pressure Gradients and Rainfall. 
Rainfall. Rainfall. 
Cape Town. Kimberley. 
Gradient. 
in. 
in. 
in. 
January 
3-864 
Ill 
3-09 
February 
3-848 
•46 
2-85 
March 
3-828 
•74 
3-06 
April 
3-838 
229 
1 57 
May 
3-832 
3-98 
•56 
June 
3-843 
433 
•26 
July 
3-845 
360 
•30 
August 
3-866 
322 
11 
September . 
3-895 
2-27 
•88 
October 
3-914 
2-27 
1 17 
November . 
3-918 
•90 
1-53 
December 
3-889 
•94 
206 
Year 
3-865 
2611 
1744 
Table II. — Monthly mean Rainfall corresponding to Synchronal Gradients 
Greater or Less than the Median. 
Rainfall. 
January 
February 
March 
April 
May 
June 
July 
August 
September 
October 
November 
December 
Summer Half 
Winter Half 
Year 
Rainfall. 
Cape 
Town. 
Kimberley. 
Small 
Large 
Small 
Large 
gradient. 
gradient. 
gradient. 
gradient. 
in. 
in. 
in. 
in. 
•87 
1-34 . 
. 3-90 
2-28 
•68 
•25 . 
. 2-72 
2-98 
•81 
•67 . 
. 2-26 
3-87 
2-20 
2 39 . 
. 1 47 
1 67 
345 
451 . 
•32 
•79 
5-67 
2 99 . 
10 
•42 
4-53 
2 66 . 
•45 
14 
3 30 
314 . 
07 
14 
2 11 
2-43 . 
•25 
1 51 
2-36 
1-92 . 
1 16 
1 13 
•99 
•81 . 
. 1-63 
1-43 
111 
•77 . 
. 1-87 
226 
6-82 
576 . 
. 13-54 
13-95 
2126 
1812 . 
2-66 
4-67 
28-08 
. 23-88 . 
. 1620 
. 18-62 
