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: