United States. Adjutant-General's Office. Military.

Military notes on the Philippines. September 1898 online

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ing layers of arsenite of copper and diabasic rocks.

5. Diorite, protogenetic gneiss, and chloric slate.

According to the judgment of Senor Jordana, the coral lime
rock is of recent formation, as it contains in abundance rem-
nants of coral and organic remains belonging to species that
live at present in the Indian Ocean. The tophus and tophic
gravel are of more ancient origin than the coral reef. The
fundamental rocks are the diabase, gabbro, sienite, diorite,
arsenite of copper, and protogenetic gneiss.

It is supposed that the western part of Luzon was prima-
rily composed of a ridge of crystalline slate, which was subse-
quently di-splaced by violent eruptions of sienite and diabase,
the fragments of which constitute the basis of a formation of
sti-ata of gravel and rock. A long period of time will proba-
l)ly pass before the volcanoes renew their activity. However
late or early this may occur, great masses of tophus will have
to form on the western coast, as it will require a long period
of submersion before such enormous sediments can be depos-
ited. During this period of rest the corals may develop their
activity in small spaces and will form, with the remains of
the floating vegetation of the continent, loam containing vege-
table fossils. Before the end of the period of submersion, the
volcanic activity must cease and the corals form on the sub-
marine tophus reefs parallel to the coast. It is probable that
the western V(jlcanic region is jn'olonged toward the south in


order to join the eastern. The information to be had on the
geological composition of these islands is very incomplete.

Eastern Volcanic Region. — The principal point is the
volcano Maj^on, still in activity, of a conic form, and having,
according to Jagor, an altitude of 8,980 feet. In the northeast
rises Monnt Mazaraga, composed of dolerite. Along the bed
of the Rio Vicol there extend toward the north highly devel-
oi^cd volcanic formations, while toward the south the soil is
composed of limy loam, containing a large amount of fossils.
The volcanic zone is prolonged by Mount Malinao, the Iriga,
and the Isarog. The first is composed of dolerite rock, the
second of dolerite and olivenite, and the third of andesite and
hornblende. The eastern volcanic region is prolonged in the
province of Camarines Norte by the Sierra Colasi and Mount
Lab(5o. Conchiferous lime, andesite, and trachyte are most
abundant in this region. A mountain ridge extends from the
western frontier of the ]3rovinces of Camarines Norte and
Camarines Sur to the Banajao Mountain, which is an extinct
volcano. Tophus, yellow lime, banks of hornblende, andesite,
and coral lime, as well as coral reefs, abound in this part of
the country. From Isarog toward the north-northwest the
volcanic zone gradually disappears and dips into the waters
of the Pacific Ocean. In the extreme east of the northern
coast of Luzon is situated the volcano Cagua, to the north of
which rises the Camiguin volcano, situated on an island bear-
ing the same name. To tlie southeast of Mayon runs the
Sierra Pocdol, also of volcanic origin. In the same direction
is situated Mount Bulusan, which from time to time ejects
sulj)hurous and watery vapor. In the south the volcanic re-
gion dips under the waters of the sea to reapj^ear in the
Dagami ridge. In the west are situated the islands of Cebu
and Bohol, surrounded by reefs of living madrepores. In the
interior of the island of Cebu is found an azure-colored lime,
in which are embedded layers of clayish slate and gravel alter-
nating with layers of coal.

In the island of Samar are found beds of ferruginous clay.
On that of Majaba appears volcanic tophus, and in the vicinity
of Loquilocum there are deposits of coal. The eastern vol-
canic region traverses the island of Camiguin, situated to the
north of Mindanao. There is a volcano in this island, which
appeared in 1871. The formation of which the island of
Mindanao is composed is not well known, but there are many


iiiclicatioiis of a volcanic origin. Williin tlie eastern volcanic
region are two volcanoes — tlie Apo, having an altitude of
10,832 feet, and still in activity, and the Saraugani, which is


The disposition of the mountain ranges in parallel chains
affords space for the development of streams both in Luzon
and Mindanao. The larger islands contain inland seas, into
which pour countless small streams from the inland hills.
Many of them open out into broad estuaries, and in numer-
ous instances coasting vessels of light draft can sail to the
very foot of the mountains. Rivers and inland lakes swarm
witli varieties of fish and shellfish. By reason of Spanish
restrictions, but little can be said as to the character of the
stream banks and beds. Four of the rivers are navigable,
and, by the statements of those who have spent some little
time on the islands, most are fordable. Drinking water is
obtained by many of the towns from the rivers at points just
above tide limits, and the water is said to be good. Bridges
are few and crude, but are generally built to Avithstand heavy

The island of Luzon abounds in rivers and streams. The
following are the principal water courses :

Rio Grande de Cagaydn, the source of which is in the
northern slope of the Caraballo Norte. It has numerous
affluents, among others the Magat and Bangag, and, after a
course of about 200 miles, falls into the China Sea in the
vicinity of Aparri.

Agno Grande starts in the north, in the neighl^orhood of
the ranch of Loo, receives the affluents Tarlag and Camiling,
as well as many others, has a course of about 112 miles, and
falls into the Gulf of Lingayen.

Abra has its origin on the opposite slope to that where Agno
Grande takes its rise ; runs for about 87 miles, and, after re-
ceiving the affluent Suyoc, divides into three arms and falls
into the China Sea over the sand bars of Butao, Nioig, and

Rio Grande de la Pampaiiga is called Rio Chico up to the
lake of Canasen, near Arayat, where it changes its name after
its junction with Rio Gapan. Its course is a little over 38
miles; it receives the Rio de San Jos^ and divides into a multi-
tude of arms as it falls into the sea to the north of Manila Bay.


V Rio Pasig has its source in the Bay Lagoon, and falls after a
course of 19 miles into Manila Bay.

Rio Vicol starts in the province of Camarines Sur and
divides into two arms, one of which falls into the lake of
Bato and the other into the spacious bay of San Miguel.

The island of Mindanao has :
^ Rio Agusan or Buhkm, almost as important a river as Rio
Grande de Cagayan with regard to its volume and length —
236 luiles. It starts near the gulf of Davao and falls into
that of Buluan.

Polangui, beginning at the foot of the volcano of Apo, runs
toward the peak of Randaya and falls into the bay of Illana,
after a course of 87 miles.

Ltibungan, falling into the gulf of Dapitan.

Iligan, falling into the bay of the same name.

The island of Paragua has many streams, but all of them
have but a short course.

The island of Samar has the following :

Oras, having a course of 24 miles and falling into the gulf
of Uguis on the Pacific.

Suribao, falling into the Pacific near Borongan.

Biiruhdn, having a course of 19 miles.

Bato-Lagudn, Basey, Calayog, Timonini, Antiyao, and
many others.

The island of Panay has the following :

Rio Panay, starting in the eastern branches of the Tapas
Mountains, runs for o8 miles and terminates its course near

Rio Acldn starts at the foot of Mount Opao and terminates
at the city of Calivo, a course of 45 miles.

Rio Taland, with the affluents Lambunao and Passi, rises
on the southern slope of the Tapas Mountains and terminates
in the vicinity of Dumangas.

Rio Salog, which rises in the mountains of Maasim, receives
the affluents Tigum and Ayuman and disappears in the vicin-
ity of Iloilo.

Rio Dalands, rising in the ridge dividing the district of
Antique from that of Iloilo, has a rapid course of 24 miles
and falls into the sea between Barbara and Tibiao.

Sabalon has an impetuous course of 08 miles.


The island of Mindoro possesses a nniltitude of streams,
but they are of small im])(n"tance. Among them are the
following- :

Navulunn, traversing the island from north to south.

Pula, in the district of Pola.

Manjao, between Tiding and Bulalacao.

In the island of Leyte are the following :

Maya, beginning in the lake of Bito and falling into the
Pacific Ocean, after a course of 31 miles.

Barauen, rising to the south of the Dagami Mountains,
runs as far as the city of the same name,

Bito, starting from the lake of the same name, terminates
near Abayog.

Leyte, starting from a lake in the west of Jaro, falls into
the sea in the Yicinity of the city of the same name.

Maasi, having a course of more than 28 miles, has its
origin in the mountain of the extreme south of the island
and terminates at GigantigJin.

Rio Cantiling, Tananau, Amilao, and others.

On the Negros island :
' Eio Danao, of great depth and breadth.

Marianas, with a wide arm named Tanao, which falls into
the sea on the northern coast.

Hinigaran, Himamaildn, and Hog, falling on the western

San Enrique, Cadiz Nuevo, and several others.

In the island of Cebu are the following :

BaJumhan, Gim, Mananga, Naga, and Sampandn.

On the island of Masbate are :

Rio Asit and Laudn, having their origin in the Bagasim-
bahan Mountains.

The island of Bohol has a multitude of streams, the greater
part of which are very short. Among others are the fol-
lowing :

Manaba, Masin, Calidian, and Napo.

The island of Catanduanes has very small rivers. The
most important of them are :

Bato, Himoto, and Tinago.

On the island of Polillo are :

Monleo, Upata, and others.



The immense coast line of the islands contains a great num-
ber of good harbors, but as a consequence of the exclusive
policy of the Spanish Government in closing them to foreign
commerce, very little is known except to coastwise naviga-
tors. Trade is confined chiefly to Manila, Iloilo, Cebil, and
Sual. Zamboanga, on the island of Mindanao, is also an
open port.

The Bay of Manila, one of the finest in the world, is about
120 miles in circumference, with very few dangers to naviga-
tion. (See plan of Manila on separate map.)

There are two long piers running out from the mouth of
the Pasig River, one terminating iii a light-house and the
other in a small fort. In stormy weather safe anchorage is
found off Cavite some S miles to the southwest by water. At
that point is found the naval establishment, including a.
marine railway, capable of taking from the water vessels of
2,000 tons displacement, and a dock for small -vessels.

Iloilo, the second port in importance, is on the island of
Panay, near its southeastern extremity and about 250 miles
in a direct line from Manila. Well-protected and naturally
good anchorage for large vessels is found outside the mouth
of the Iloilo River, but small vessels enter it and discharge
cargoes at the town wharves.

Of the interior roads little can be said, and of those run-
ning along the coast positive information is not available.

Roadbeds are generally fair and easy during the dry sea-
son and average about 25 feet in width. Some are ditched
and graded, but very little metal has been placed upon them,
and in the wet season road transportation is almost impossi-
ble. During the latter season transportation by roads is car-
ried on by means of rude sledges drawn by buffalo — a sort of
sleighing on mud.


The extreme length of the Philippine group being from
north to south, their northern extremitj^ reaching to the
northern limit of the tropical zone, causes a considerable
variety of climate. However, the general characteristics are


In the region of Manila the hottest season is from Mart-h to
June, the greatest heat being felt in May before the rains set
in, when the maximum temperature ranges from 80° to 100°
in the shade. The coolest weather occurs in December and
January, when the temperature falls at night to 60° or 65°
and seldom rises in the day above 75°. From November to
February the sky is bright, the atmosphere cool and dry, and
the weather in every way delightful. Observations made at
the Observatorio Meteorologico do Manila have been compiled
by the U.S. Weather Bureau, covering a record of from sev-
enteen to thirty-two years, from which the following is an
extract :

Temperature, degrees F. :

Mean annual 80°

Warmest month. 82

Coolest montli _- 70

Highest 11)0

Lowest - - GO

Humidity :

Relative per cent 78

Absolute grains per cubic foot 8.75

Wind movements in miles :

Daily mean -__ -__ 134

Greatest daily. 204

Least daily 95

Prevailing wind direction— NE. , November to April; SW., May
to October.

Cloudiness, annual per cent 58

Days with rain 135

Rainfall ni inches :

Mean annual 75. 43

Greatest monthly 120.98

Least monthly _ - - 55. 65

The following is the mean temperature for the three seasons,
at points specified :

Cold. Hot. Wet.

Manila 72' 87' 84

Cebu .- 75 86' 75°

Davao. 86' 88' 87'

Sulu 81' 82' 83°

Seasons vary with the prevailing winds (monsoons or trade
winds) and are classed as "wet" and "dry." There is no
abrupt change from one to the other, and between periods
there are intervals of variable weather.

The Spanish description of seasons is as follows:

Seis meses de lodo — six months of mud.


Seis meses de polvo — six months of dust.

Seis iiieses de todo — six months of everything.

The northern islands lie in the track of the tj'phoons wliich,
developing in the Pacific, sweep over the China Sea from NE.
to SW. during the southwest monsoon. They may be looked
for at any time between May and November, but it is during
the months of July, August, and September that they are
most frequent. Early in the season the northern region feels
the greatest force, but as the season advances the typhoon
gradually works southward and the dangerous time at Manila
is about the end of October and the beginning of November.
Typhoons rarely, if ever, pass south of 9° N. latitude. Some-
times the typhoon is of large diameter and travels slowly, so
far as progressive motion is concerned ; at others it is of smaller
dimensions, and both the circular and progressive motions
are more rapid. However, they are always storms of terrific
energy and frequently cause terrible destruction of crops and
property on shore and of shipping at sea. Thunderstorms,
often of great violence, are frequent in May and June, before
the commencement of the rainy season. During July, August,
September, and October the rains are very heavy. The rivers
and lakes are swollen and frequently overflow, flooding large
tracts of low country.

At Manila the average rainfall is stated to he from 75 to
120 inches per annum, and there the difference between the
longest and shortest day is only 1 hour 47 minutes and 12
seconds. This rainfall, immense though it be, is small as
compared with that of other parts of the archipelago ; e. g.,
in Liano, NE. of Mindanao, the average yearly downpour is
142 inches.


The gales of the Philippines may be divided into three
classes, known by the local names of Colla, Nortada, and
Bagnio. The Colla is a gale in which the wind blows con-
stantly from one quarter, but with varying force and with
alternations of violent squalls, calms, and heavy rains, usu-
ally lasting at least three days ; these gales occur during the
southwest monsoon and their direction is from the southwest
quarter. The Nortada is distinguished from the Colla, in
that the direction is constant and the force steady, without
the alternations of passing squalls and calms. The Nortada
is generally indicative that a tyi")lioon is passing not very far


off. These gales occur cliieiiy in 11m' iioilliri-n islands, and
their direction, as the name implies, is from the northward.
Baguio is the local name for the revolving storm known as
the typhoon, which, heing the more familiar term, will he
nsed in these notes.


These storms have their origin to the east or to the south-
east of the Philippines, whence their course is westward,
with a slight divergence to the north or south, the average
direction appearing to be west by north. They occur in all
months of the year, but the greater number take place about
the time of the equinoxes. The most violent ones occur at
the autumnal equinox, and on an average, two or three occur
every year, and sometimes one follows another at a very
short interval. It is believed that when one of these typhoons
passes in a high latitude in September there will be another
in r)ctol)er of that year, and one maybe looked for in Novem-
ber in a lower latitude. These tempests are not encountered
in latitudes below 9° N. The rate of progress of these storms
is about 13 miles an hour; in none of those observed has it
exceeded 14 miles nor fallen below 11 miles. The diameter
of the exterior revolving circle of the storm varies from 40
to 130 miles, and the diameter of the inner circle, or calm
region, may be estimated at from 8 to 15 miles. The duration
of the true typhoon at any one place is never longer than ten
hours and generally much less. These storms are always
accompanied by abundant rain, with low, dense clouds, which
at times limit the horizon to a few yards distance, and are
generally accompanied by electrical discharges. The barom-
eter falls slowly for some days before the typhoon, then falls
rapidly on its near approach, and reaches its lowest when
the vortex is but a little way off. It then rises rapidly as the
vortex passes away, and then slowly when it has gained some
distance. Near the vortex there are usually marked oscilla-
tions. The typhoon generally begins with a northerly wind,
light drizzling rain, weather squally and threatening, a fall-
ing barometer and the wind veering to the eastward, when
the observer is to the northward of the path of the storm,
and backing to the westward when he is to the southward of
it ; the wind and rain increase as the wind shifts, and the
storm generally ends with a southerly wind after abating


Tlie following warnings of tlie approach, of a typhoon, and
directions for avoiding the most daugerons part of it, are
taken from tlie China Sea Directory : The earliest signs of a
typhoon are clouds of a cirrus type, looking like fine hair,
feathers, or small white tufts of wool, traveling from east or
north, a slight rise in the barometer, clear and dry weather,
and light winds. These signs are followed by the usual ugly
and threatening appearance of the weather which forebodes
most storms, and the increasing number and severity of the
gusts with the rising of the wind. In some cases one of the
earliest signs is a long heavy swell and confused sea, which
comes from the direction in which the storm is approaching,
and travels more rapidly than the storm's center. The best
and surest of all warnings, however, will be found in the
barometer. In every case there is great barometric disturb-
ance. Accordingly, if the barometer falls rapidly, or even
if the regularity of its diurnal variation be interrupted, dan-
ger may be apprehended. No positive rule can be given as to
the amount of depression to be expected, but at the center of
some of the storms the barometer is said to stand fully 2 inches
lower than outside the storm field. The average barometric
gradient, near the vortex of the most violent of these storms,
is said to be rather more than 1 inch in 50 nautical miles. As
the center of the storm is approached the more rapid become
the changes of wind, until at length, instead of its direction
altering gradually, as is the case on first entering the storm
field, the wind flies around at once to the opposite point, the
sea meanwhile breaking into mountainous and confused heaps.
There are many instances on record of the wind suddenly fall-
ing in the vortex and the clouds dispersing for a short inter-
val, though the wind soon blows again with renewed fury.

In the northern hemisphere when the falling barometer and
other signs create suspicion that a typhoon is approaching,
facing the wind and taking 10 or 12 points to the right of it,
will give the approximate bearing of its center. Thus, with
the wind NE., the center will probably be from S. to SSE. of
the observer's position. However, it is difficult to estimate the
center of the vortex from any given point. This j)artly arises
from the uncertainty as to the relation between the bearing
of the center and the direction of tlie wind, and greatly from
there being no means of knowing whether the storm be of
large or small dimensions. If the barometer falls slowly, and


the weather grows worse only grcidiially, it is reasonable to
suppose that the storm center is distant; and conversely, with
a rapidly falling barometer and increasing bad weather the
center may be supposed to be approaching dangerously near.

Practical Rules. — When in the region and in the season
of revolving storms, be on the watch for premonitory signs.
Constantly observe and carefully record the barometer.

When on sea and there are indications of a typhoon being
near, heave to and carefully observe and record the changes
of the barometer and w^ind, so as to find the bearing of the
center, and ascertain by the shift of the wind in which semi-
circle the vessel is situated. Much will often depend upon
heaving to in time. When, after careful observation, there
is reason to believe that the center of the typhoon is approach-
ing, the following rules should be followed in determining
whether to remain hove to or not, and the tack on which to
remain hove to :

In the northern hemisphere, if in the right-hand semicircle,
heave to on the starboard tack. If in the left-hand semicircle,
run, keeping the wind if possil)le, on the starboard quarter,
and when the barometer rises, if necessary to keep the ship
from going too far from the proper course, heave to on the
]3ort tack. When the vessel lies in the direct line of advance
of the storm — which position is, as previously observed, the
most dangerous of all — run with the wind on the starboard
quarter. In all cases increase as soon as possible the distance
from the center, bearing in mind that the whole storm field
is advancing.

In receding from the center of a typhoon the barometer will
rise and the wind and sea subside. It should be remarked
that in some cases a vessel may, if the storm be traveling
slowly, sail from the dangerous semicircle across the front of
the storm, and thus out of its influence. But as the rate at
which the storm is traveling is quite uncertain, this is a
hazardous proceeding, and before attempting to cross the sea-
man should hesitate and carefully consider all the circum-
stances of the case, observing particularly the rate at which
the barometer is falling.


The waters of the Pacific Ocean between the parallels of
26° S. and 24^ N. have a regular motion from east to >vest,
which is known as the equatorial current. This, at a little


to the nortliward of tlie Equator, a])pears to be divided into
the north and south equatorial currents by the equatorial
countercurrent, a stream flowing from west to east through-
out tlie Pacific Ocean. The currents in the western part of
the Pacific, to the nortliward of the Equator, are affected by
the monsoons, and to the southward of the Equator they are
deflected by the coast of Australia.

The trade drift, which flows to the westward between the
parallels of 9° and 20° N., on reaching the eastern shores of
the Philippine Islands again turns to the northward, forming
near the northern limit of that group the commencement of
the Japan stream. The main body of the current then flows
along the east coast of Formosa, and from that island pur-
sues a northeasterly course through the chain of islands lying
between Formosa and Japan ; and sweeping along the south-
eastern coast of Japan in the same general direction, it is
known to reach the parallel of 50° N". The limits and velocity
of "the Japan stream are considerably influenced by the mon-
soons in the China Sea, and by the prevailing winds in the
corresponding seasons in the Yellow and Japan seas; also by

Online LibraryUnited States. Adjutant-General's Office. MilitaryMilitary notes on the Philippines. September 1898 → online text (page 2 of 31)