acres of land covered with shallow water the last of October, 1902, just at the end of the dry season of the Cagayan Valley.  The surface was well covered with rank, coarse grasses and filled with aquatic plants, especially with lilies.  Apparently the waters were slowly receding, since the earth about the margins was supporting the short, coarse grasses that tell of the gradual drying out of soils once covered with water.  In the mountains near Sagada, Bontoc Province, there is a very small lake, and one or two others have been reported at Bontoc; but the mountains must be said to be practically lakeless.

Another mountain range of northern Luzon, of which practically no details are known, is the Sierra Madre, extending nearly the full length of the country close to the eastern coast.  It seems to be an unbroken, continuous range, and, as such, is the longest mountain range in the Archipelago.

The fourth type of surface is the level areas.  These areas lie mainly along the river courses, and vary from a few rods in width to the valley of the Rio Grande de Cagayan, which is often 50 miles in width, and probably more.  There are, besides these river valleys, varying tracts of level plains which may most correctly be termed mountain table-lands.  The limited mountain valleys and table-lands are the immediate home of the Igorot.  The valleys are worn by the streams, and, in turn, are built up, leveled, and enriched by the sand and alluvium deposited annually by the floods.  They are generally open, grass-covered areas, though some have become densely forested since being left above the high water of the streams.

The broad valley of the Rio Grande de Cagayan is not occupied by the Igorot.  It is too poorly watered and forested to meet his requirements.  It is mainly a vast pasture, supporting countless deer; along the foothills and the forest-grown creek and river bottoms there are many wild hogs; and in some areas herds of wild carabaos and horses are found.  Near the main river is a numerous population of Christians.  Many are Ilokano imported originally by the tobacco companies to carry on the large tobacco plantations of the valley, and the others are the native Cagayan.

The table-lands were once generally forested, but to-day many are deforested, undulating, beautiful pastures.  Some were cleared by the Igorot for agriculture, and doubtless others by forest fires, such as one constantly sees during the dry season destroying the mountain forests of northern Luzon.

General observations have not been made on the temperature and humidity of much of the mountain country of northern Luzon.  However, scientific observations have been made and recorded for a series of about ten years at Baguio, Benguet Province, at an altitude of 4,777 feet, and it is from the published data there gathered that the following facts are gained.[7] The temperature and rainfall are the average means deduced from many years’ observations: