506 
Philippine Journal of Science 
1919 
humidity should also be fairly high. Such a climate is found 
only over limited areas within a few degrees on either side of 
the equator. 
The amount and distribution of rainfall in the southern part 
of the Philippine Archipelago appears to be quite suitable for 
Hevea brasiliensis. Table II gives the rainfall at Isabela, Ba- 
silan Island, by months, with the number of rainy days in each 
month, over a period of eleven years. 
During the period mentioned the average rainfall at Isabela 
has been 1,794.1 millimeters, with a minimum occurring in 1905 
of 1,103 milimeters. During this time there have been but three 
months entirely without rain, though there is a dryer season 
during January, February, and March. The number of rainy 
days during the period under consideration has averaged 153.1, 
with a minimum of 112 in 1905. 
In Table III are given the average rainfall and the number of 
rainy days at a number of other stations in the southern part 
of the Philippines. 
Table III. — Rainfall data for the southern Philippine Islands, 1903-1913. 
[Rainfall is given in millimeters.] 
Month. 
Jolo. 
Davao. 
Cotabato. 
Zamboanga. 
Rainfall. 
Rainy 
days. 
Rainfall. 
Rainy 
days. 
Rainfall. 
Rainy 
days. 
Rainfall. 
Rainy 
days. 
January 
89.1 
7.4 
110.2 
5.9 
98.8 
12.6 
37.2 
4.9 
February 
122.4 
7.4 
141.6 
7.6 
88.8 
10.1 
62.0 
6.1 
March 
85.2 
8.1 
164.2 
7.6 
68.1 
7.8 
21.0 
2.6 
April - . 
118.2 
7.3 
190.3 
9.2 
164.9 
12.7 
38.2 
5.6 
May -- 
160.2 
13.5 
252.8 
11.6 
218.5 
14.7 
72.0 
7.6 
June 
203.3 
16.0 
234.2 
11.0 
237.3 
17.2 
88.8 
10.6 
July 
172.0 
12.2 
208.9 
10.2 
292.0 
18.4 
90.0 
10.6 
August 
170.4 
13.9 
207.4 
10.1 
271.8 
18.4 
96.0 
10.9 
September 
184.4 
12.5 
203.6 
9.8 
248.6 
16.7 
106.3 
9.6 
October 
222.9 
16.1 
242.3 
11.6 
255.1 
15.3 
116.1 
10.1 
November 
193.0 
14.5 
176.4 
9.2 
231.7 
!5.9 
106.6 
9.4 
December 
144.8 
14.4 
208.8 
10.1 
133.6 
13.0 
84.3 
8.1 
Total 
1,865.9 
142.3 
2.340.7 
113.7 
2,309.1 
172.8 
926.4 
94.8 
The rainfall at Zamboanga is the lightest recorded for any 
station in the Philippines and is given here solely for the pur- 
pose of showing the variation in rainfall that may occur within 
a comparatively short distance. Zamboanga is separated from 
Basilan by a strait but a few kilometers wide. In a range of 
hills only a few kilometers back of Zamboanga the rainfall is 
again much heavier. Davao has the heaviest and most evenly 
