18 
Tra7isactions of the Royal Society of South Africa. 
across the Indian Ocean ; the second depends upon the fact that Antarctic 
ice moves east-north-east in the current that laves the west coast of South 
Africa. Thus a knowledge of the conditions at Durban, or in the South 
Orkneys, will enable us to give a pretty fair forecast of what is to come in 
Mauritius or in Kimberley respectively. 
The object of this slender communication is to show how, in such a 
climate as ours, the meteorological elements of one month may be modified 
by those of the month before, and hence that it may become possible to 
predict in general terms the character of a coming season or period. The 
elements selected for this purpose are the rainfall of the second half of May 
and the temperatures of June. 
In Table I, col. 1 gives the year ; 
Col. 2, the rainfalls of May 16-31 ; 
Col. 3, the deviation signs, plus or minus, from the average of the 
fourteen years 1904-1917 ; 
Cols. 4 and 5, the mean minimum temperatures of the air and the lowest 
temperatures observed ; 
Cols. 6 and 7, the mean minimum temperatures on grass and the lowest 
temperatures observed ; 
Col. 8, the mean maximum temperatures of the air ; 
Cols. 9 and 10, the rainfalls of June and the number of rain days in 
June, for comparison. 
Table I. — May Rainfall and Jime Temjjeratures. 
Year. 
Rainfall, 
May 
16-31, 
Rainfall 
devia- 
tion. 
Mean 
minimum 
tempera- 
ture 
of the air 
Lowest 
tempera- 
ture 
of tlie air. 
Mean 
minimum 
temi^era- 
ture 
on grass. 
Lowest 
tempera- 
ture 
on srrass. 
Mean 
maximum 
tempera- 
ture 
of the air. 
Rainfall, 
June. 
Rain 
days, 
June. 
Degrees 
Deo-rees 
Desrees 
Degrees 
Degrees 
In. 
Fahr. 
Fahr. 
Fahr. 
Fahr. 
Fahr. 
In. 
1904 
•005 
36-2 
24-6 
25-2 
12^4 
65-6 
•427 
6 
1905 
•605 
34-4 
26-3 
24-2 
15'4 
63-2 
-005 
1 
1906 
•620 
37-1 
28-0 
26-9 
17^2 
65-9 
•030 
2 
1907 
•725 
+ 
37-6 
26^8 
26-6 
14^6 
65-6 
•060 
3 
1908 
•140 
35-1 
26^1 
240 
13-2 
65-3 
•430 
1 
1909 
1-210 
+ 
39-8 
31-8 
28-8 
20-6 
66-7 
1910 
•060 
34-7 
26-0 
22-5 
13-7 
63-2 
•255 
4 
1911 
1^510 
+ 
36-4 
260 
25-6 
14-7 
61-1 
•850 
3 
1912 
1-950 
+ 
36-0 
30-0 
26-4 
19-5 
62-2 
•395 
2 
1913 
•000 
38-2 
28-6 
28-6 
17^7 
651 
•355 
3 
1914 
1-600 
+ 
36-9 
27^0 
27-6 
18-5 
62-4 
•665 
2 
1915 
-735 
+ 
37-6 
24-0 
27-4 
15.7 
65-2 
•400 
4 
1916 
-000 
34-1 
27-0 
20-5 
13^5 
66-5 
1917 
35-0 
24-7 
22-7 
10^3 
63-1 
•325 
5 
Aver- 
ages 
-654 
36^4 
26-9 
25^5 
15-5 
64-4 
