ECOLOGICAL CHARACTERISTICS OF MARIANA ISLANDS. 13 
especially in the southern half of the island; it was found in Tahiti that the average 
temperature diminished to the extent of 5° C. for every thousand feet of added 
height. The uplands of Guam are by no means as lofty as the great mountains of 
Tahiti, and the same general scale might not hold in the present instance; yet expe- 
rience proves that the temperature of the hills is lower than that of the coasts. Mak- 
ing all due allowances, however, it is justifiable to conclude that the temperature 
deviations are not very great in degree, while the seasonal cycle would assuredly 
be the same in kind in all parts of Guam as well as in the neighboring islands which 
are inhabited by Partule. 
TABLE 3.—Statistics of rainfall for 1902 at Agana, Guam (after Safford). 



Inches. Millimeters. Number of days with rain. 
ele ee ee ee ee ee Percentage 
Month. of annual 
Total. | Maximum) Tota], | Maximum rainfall. | More than| More than| More than} More than 
in 24 hours. in 24 hours. a trace. 0.1 inch. | 0.5 inch. 1 inch, 

PpaMrlar ys asf. 2 os 3.58 1.01 90.93 25.65 $5 18 11 2 
February...... 7.30 2.24 185.42 56.90 6.3 21 9 4 
WYATCH sco «| osod 0.90 81.53 22.86 2.8 16 9 2 
EDEN Aad. 2's <b Sts 3.87 0.71 98.04 18.03 Siok 19 11 3 
IVTAY i okcists, 353% 4.55 0.92 115.57 23.37 3.9 22 9 3 
NUE eyes ie. 3 7.14 2.92 181.36 74.17 6.1 25 12 4 
PO chs ite ss 16.06 6.26 407.92 159.00 13.8 28 17 7 
AUgUst is... 19.72 4.72 500.89 119.89 16.9 28 23 12 
September.....| 27.01 2.34 686.06 134.87 23.2 2% 26 15 
October... 7%. 9.63 2.81 244.60 OL oi 8.3 21 12 7 
November..... 11.86 2.62 301.24 66.55 10.2 25 17 6 
December..... Pe SS 0.77 64.26 19.56 FI. 15 9 1 
Summary...|/116.46 et. 2e95S<12: |p oe. 28 100.0 265 165 66 
Maximum..... 27.01 6.26 686.06 159.00 23.2 28 26 15 
Minimum..... Zoe para O40 20 ee Phe 15 9 1 





Passing now to the subject of rainfall, the basis of fact is provided by the figures 
for the representative year of 1902, as given by Safford from Abbe’s reductions; 
these are presented in somewhat modified from in table 3. As in the case of tem- 
perature, there is a long annual cycle with September as the month of greatest 
rainfall. The nadir of this cycle is not so clearly marked, but it occurs during the 
earliest months of the year. It is not proper to speak of a “dry” season in view of 
the fact that some rain was recorded on about half of the days during the months 
of less precipitation; the alternating seasons are the “wet’’ and the “less wet.” 
The figures are exceptionally consistent; September is the month of greatest rainfall, 
it has the greatest number of days with more than o.1 inch, of more than 0.5 inch, 
and of more than 1 inch, despite the fact that rain fell on 27 days as compared with 
the 28 days of August or July. 
Without question local variations in precipitation occur, like regional fluctua- 
tions in temperature; the slopes of the mountains in the southern half of Guam 
receive much more rain than Agafia or the northern plateau. Yet the local varia- 
tions must be far less in amplitude than in a large land-mass like Tahiti, for in 
Guam the mountains are not sufficiently high to prevent the heavier storms from 
passing over their peaks from the windward to the leeward side of the island. 
