A Contribution to the Study of the Rainfall Map of South Africa, 383 
Table B. — Miscellaneous Details of Bainfall. 
Section. 
Average number 
of rainy days 
Greatest 
rainfall in 
one year, 
(inches). 
Heavy rainfall in 24 hours. 
per a nnum. 
I 
152 
12618 
6-00 at Newlands. 
II 
110 
115-47 
. 5-93 , 
, Berg Elver. 
III 
75 
34-60 
. 3-14 , 
, Dassen Island. 
lY 
138 
69-27 
. 16-50 , 
, Swellendam. 
V 
59 
28-12 
. 4-63 , 
, Kleinpoort. 
YI 
51 
47-26 
. 5-00 , 
, Zwartberg Pass. 
YII 
92 
4417 
4-60 , 
, Somerset East. 
YIII 
70 
34-81 
. 4 30 , 
, Petriisville. 
IX 
70 
38-47 
. 4-60 , 
, Campbell. 
X 
152 
103-11 
. 11-33 , 
, Evelyn Yalley. 
XI 
101 
56-53 
. 5-94 , 
, Ellesmere. 
XII 
130 
68-54 
9-29 , 
, Flagstaff. 
XIII 
96 
49-19 
. 4-25 , 
, Mafeteng. 
XIY 
43-29 
XY 
162 
73-00 
. 17-45 , 
, Umzinto. 
XYII 
60 
28-44 
5-20 , 
, Yryburg. 
XIX to XXIII 
86 
4-09 
, Pretoria. 
XXIY 
77 
45-30 
. 5-45 
, Grwels. 
XXY 
100 
72-15 
XXYII 
123 
The average precipitation for each hour is given under the heading 
*' Quantity." The driest hour of the day is 9 to 10 a.m. v^ith scarcely more 
than a quarter of an inch a year ; the wettest hour is 4 to 5 p.m. with six 
times as much. The hourly quantities are somewhat irregular, probably 
because 17 years is too short a period to produce a smooth curve. 
The numbers under the heading Eate " specify the average hourly 
intensity of rainfall. It is deduced by dividing the whole fall per hour per 
annum by the number of hours it took to fall in, or — 
Quantity / frequency = rate. 
We see that the hourly average rate of rainfall in wet weather rises and 
falls as the hourly average frequency increases and diminishes — that is to say, 
the hour which carries the greatest chance of rain carries the heavier fall 
when it comes. The lightest rain comes between 7 and 11 a.m., the heaviest 
in the afternoon. 
In Table B some miscellaneous details of rainfall are given, taken mainly 
from the records of the twelve years 1897 to 1908. The " Average number 
of rainy days " does not, excepting in a few instances, apply to any one 
station in a particular section, but is really the average of the greatest 
33 
