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TABLE 50.—Orientation of the thunderstorms observed in Manila during the period

YEAR.

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YEAR.

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3

9

27

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JUNE.

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YEAR.

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YEAR.

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4th

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As can be seen by the monthly totals which we give, thunderstorms are least frequent in the third quadrant, the only exceptions being in the months of February, November, and December, in which the second quadrant shows a smaller total. The greatest frequency has been observed in the first quadrant in the months of May, July, August, September, October, and December, and in the fourth quadrant in the months from January to April, inclusive; in the second in June, and in the third in November.

The yearly totals for the ten years are distributed also as to the different orientation in the following outline:

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The results in all cases are identical with those obtained by Father Saderra regarding the thunderstorms during the first five years; that is, the greater number, 1,408, corresponds to the first quadrant; the intermediate, 1,349, to the fourth quadrant, and the other two, 1,246 and 1,025, to the second and third quadrants, respectively.

This relates merely to the location of thunderstorms in general, irrespective of other classification. Let us consider the location (orientation) of the different classes of thunderstorms, of which we give the following outline:

YEAR.

THUNDERSTORMS T.

THUNDERSTORMS L.

THUNDERSTORMS R.

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As seen by this outline, we have 332 thunderstorms T, of which 139 belong to the first quadrant, 90 to the second, 63 to the fourth, and 40 to the third. Of the 1,755 thunderstorms L, the smallest number (315) belong to the third quadrant, and the greatest number (577) to the first quadrant, there being a notably small difference between those of the second (436) and those of the fourth (428). The distribution of the 2,963 thunderstorms R in the four quadrants is sufficiently different. The maximum (858) belongs to the fourth; following this, in descending order, the second, first, and third (722, 692, and 690). The observations given in the preceding pages refer to stations placed below 80 meters of altitude above the mean sea level. On the other hand, the climatological elements of a station situated 4,777 feet above the mean sea level will give an idea of the climate of other similar altitudes, for instance, those of Lepanto-Bontoc, province of Abra, Benguet, Cavite, and Tayabas. Highlands in the island of Mindanao, as around Lake Lanao, the mountain region of CagayánMisamis and of Surigao, have also similar climatic features, except that the rain is here more evenly distributed than in the high plateaus of Luzón.

The temperature in Benguet is very remarkable, and is lower than the average of other corresponding altitudes. This fact is due chiefly to the prevailing westerly and southwesterly winds during March, April, May, and June, the hottest season of the year in the archipelago, as pointed out in the preliminary notes.

TABLE 51.-Climatic elements in Baguió (Benguet).

[Altitude, 4,777 feet above mean sea level.]

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III. VOLCANOES AND SEISMIC CENTERS.

Situation and Nature of the Archipelago-Active and Dormant Volcanoes--Historical Geology-Earthquakes-Observation of Seismic Disturbances-Volcanoes and Earthquakes in Mindanao and the Visayas-In Southeastern, Central, and Northern Luzón-Relative Frequency of Earthquakes.

BY REV. M. SADERRO MASÓ, S. J.,

Assistant Director of the Philippine Weather Bureau.

The number of islands which compose the Philippine archipelago is not less than 3,141, although up to the present time no one can state the exact number. All these islands are comprised within the north Torrid zone, between 4° 40′ and 21° 10′ north latitude and longitude 116° 40′ and 126° 34' east of Greenwich. They are surrounded on the north and west by the China sea, on the east by the Pacific ocean, and on the south by the sea of Celebes. From the extreme point of land on the northwest to the China coast is a distance of 230 kilometers. The nearest land on the north is the island of Formosa, on the east the Palos Islands, on the southeast the Molucca archipelago, on the south the island of Celebes, on the southwest the island of Borneo, and on the west Cochin China.

The waters which surround the archipelago are very deep, not far from the east coast the Pacific being from 4,000 to 6,000 meters in depth. The Joló sea between Mindanao and Joló reaches a depth of 4,069 meters, off the Celebes 3,750 to 4,755, and not far from the south coast of Mindanao the depth reaches 5,000 meters; nevertheless, the Philippines are united to the Asiatic archipelago at three points where the straits filled with islands reach but little depth, namely, north of Borneo by the islands of Balábac and Paragua, on the northeast of Borneo by the Joló group, and on the northeast of Celebes by the islands of Sanguir and Tulur. Without doubt, therefore, the whole of the Philippine archipelago belongs to the same geographic region as Borneo, Sumatra, Java, and the rest of the islands of the great Asiatic archipelago, and in consequence to Asia rather than to Oceania. Considering, therefore, only geographic reasons, it is sufficient to note the analogy which the situation of the Sunda Islands, the Celebes, the Moluccas, and the Philippines, with relation to Asia, bears to the situation of the Antilles with relation to America. The former bound the

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interior China and Sunda seas, the latter, the Mexican and Caribbean seas, which bathe, respectively, the Asiatic and American coasts. According to this analogy, therefore, if the latter belong to America the former belong to Asia.

1

"On the other hand," says G. F. Becker, "a glance at such a map as Stieler's physical map of Asia is sufficient to show that Borneo, Celebes, Gilolo, and the Philippines are very nearly related from a structural point of view. The southwestern ranges seem to gather in toward the eastern edge of the Philippines as do the branches of a tree to its trunk. The eastern coast range of Mindanao is continued southward by the Tulur Islands and others to Gilolo, in the Moluccas. Near the center of our own island of Leyte there is a fork in the mountain system, and the westerly branch is seemingly continued southward through Mt. Apo and the southernmost point of Mindanao, by way of Sanguir Island, to Celebes. In the Visayas, at Masbate, it would seem that a second branch is thrown off, extending through Negros and western Mindanao, Basilan, and the Joló group, to the Bornean coasts. More obscure is a line which starts apparently in Panay and is marked in the Joló sea by the Cagayanes, including Cagayán de Joló. A very important line is represented by the Calamianes and Palawan, continued in Borneo by the range, one point of which is the lofty Kina Balu, which is not volcanic. This range extends through Borneo to its southwest coast and, in the opinion of some geologists, not including Mr. Verbeck, there connects with Bangka. In northern Luzón the coast range, or Sierra Madre, is clearly continued by the Babuyanes and Batanes to the neighborhood of Formosa, but the relations of the Zambales range and the Caraballo Norte are not evident on mere inspection."

But if we turn our consideration from the apparent ridges indicated by the lined islands to the submarine features, then we shall find that the whole archipelago, excepting western Paragua, lies out of the shallow sea area, connecting the great islands of Borneo, Java, and Sumatra with the Asiatic continent. The deep sea in which our archipelago lies, runs through the Celebes and the Moluccas, between the Borneo shallow sea just spoken of and the eastern one connecting New Guinea with Australia. Therefore, it would seem that our archipelago is really connected with the Celebes and the Moluccas, all of which lie in this sort of channel dividing Asia from Australia. It may be that further investigations will show a closer similarity between our archipelago and the Celebes and the Moluccas. Recently A. Wichman has rejected the supposed homologies between Celebes and Borneo. "The mountain ranges of Borneo are ancient, while

1 Report on the Geology of the Philippine Islands, 1901.
'Malay Archipelago, Wallace, page 7.

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