r>
It, is true*, the records of the new stations do not yet cover a. sufficiently long period to give a veryaccurate normal average, but wc consider them sufficient for a fair statement. We are confirmed inthis belief by a fact observed in the long series of the Manila Observatory. On examining this serieswe find that the relatively dry periods—that is, those having an annual rainfall below the normalaverage—never lasted more than three years. Since the year 1805 such a period has occurred onlythree times, and—as a compensation, as it were, for the deficiency—the records invariably show thatthe years immediately preceding and following have been excessively rainy. 'The result is, that what-ever period of live years you choose, it will give an average very close to the normal. The same factcan likewise be observed in the shorter series of many other stations.
The average 1 annual rainfall of the Archipelago is 2,300 millimeters; the extreme values being!)00 millimeters and 4,000 millimeters. There are no large tracts of extraordinary drought. Whena relative failure of rainfall occurs, it is more or less felt throughout the Islands. In the recordsof the Observatory the year 1885 is the only one with an annual rainfall below 50 per cent of thenormal amount.
Over the greater part of the Archipelago the heaviest rainfall occurs during the summer andautumn months from .June to. October, properly called the “rainy season.” During the wintermonths, November, December, January, and February, the rains continue to fall abundantly on theeastern and northern coasts, thus constituting for the regions facing the Pacific Ocean and the largerinland seas a second rainy season. The spring months, March, April, and May, are the driest; butas tin; sun is ascending and the thermal focus traveling northward, local thunderstorms becomemore frequent throughout, the Archipelago and cause heavy showers, especially on the highlandsof the southern islands, the Yisayas and .Mindanao.
In order, therefore, to treat the subject thoroughly we must describe the yearly distribution ofrainfall in the Philippines under the following headings:
I. Summer and Autumn Rainfall; Cyclonic Rainfall.
II. Winter. Rains; Northeast Monsoon Rainfall.
III. Spring Rainfall; Thunder showers.
LIST OF PROVINCES AND NUMBER OF RAINFALL STATIONS OF THEPHILIPPINE ARCHIPELAGO.
Provinces and islands.
Numberof rain-gaugestations.
Average
rainfall.
Area of theprovince orisland.
Ratio ofarea tonumber ofstations.
Butanes Islands_ _ .. _
i
mm.
2, 860.1
Sq. miles.
64
A bra, Luzon. _ _ _ _ __
0
1,171
Cagavan, Luzon .. _ ___ _ __ .. .
2
1, 854
5, 052
1,330
2,526
Iloeos Norte, Luzon. . .... ___
0
IloeosKur, Luzon __ _ _ _ __
9
2, 304. 4
' 471
235. 5
Lepanto-Bontoc, Luzon .... ____
0
2,005
Isabela, Luzon_ ..... _
0
5, 018
1,905634
Nueva Vizcaya, Luzon _ ...
1
1,180. 2
1, 905
634
Union, Luzon __ .. _ _ ..
1
2, 266. 6
Benguet, Luzon... ... . .... ....
I
4,' 0012,441.61,901.81, 784. 5
822
822
Pangasinan, Luzon. ...
1
1,1931,0252,169868
1 193
Tartar, Luzon ....__
]
1 025
Nueva Ecija, Luzon _ __
1
2 169
Pampanga, Luzon. _ ...
2
2, 028
3, 303. 7
434
Zanibales, Luzon_ .. __ . _
4
2,125
537
531. 2
Bataan, Luzon _ ...
1
2, 349. 42,103.11,926.51, 744
537
Bulacan, Luzon. ... _. _.
]
1 173
1 173
Manila and Uizal, Luzon _ __ _. .. .
Cavite, Luzon_ __ __ _
1
3
753
619
753
206. 3
Corregidor Island.. . . ....
1
2,199. 3
2
2
Batangas, Luzon _ .....
1
L 512. 82, 061.5
1,201
629
1,201
314. 5
Laguna, Luzon . ... _ _
2
Tayabas, Luzon _ ._ __ __ __
3
2, 650. 8
5, 993
1, 997. 7
Cainarines, Luzon... _ ...
1
1, 818. 7
3, 279
3, 279
Albav, Luzon. .. ._
9
3, 045, 2
1,783
.891.5