Gales.—­The gales of the Philippines may be divided into three classes, known by the local names of Colla, Nortada, and Baguio.  The Colla is a gale in which the wind blows constantly from one quarter, but with varying force and with alternations of violent squalls, calms, and heavy rains, usually 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 typhoon is passing not very far off.  These gales occur chiefly in the northern 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, being the more familiar term, will be used in these notes.

Typhoons.—­These storms have their origin to the east or to the southeast 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 a high latitude in September there will be another in October of that year, and one may be looked for in November in a lower latitude.  These tempests are not encountered in latitudes below 9 degrees 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 barometer 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 oscillations.  The typhoon generally begins with a northerly wind, light drizzling rain, weather squally and threatening, a falling 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 gradually.