The Equatorial Region. The area covered by this region, whose exact boundaries are shown in the map on page 135, includes the Malay Peninsula and the East Indian Islands. Sumatra, Java, and Borneo stand upon the continental shelf of Asia, and are the undrowned highlands of the now submerged ‘Sunda-land’. Old lines of fold run through Malaya, the islands of Banka and Billiton, and Borneo to the Philippines, but most of this part of the region consists of the remnants of a former peneplain. Tertiary earth movements have thrown up recent folds on the west and south of Sumatra and Java and in the Philippines and have caused corresponding trenches to be formed in the sea bottom in the Java and the Tuscarora Deeps. These recent lines of folding are marked by active volcanoes and by seismic activity. Where the folds curve round in the Banda Islands, the ridges are gradually being raised above the sea, as is proved by the presence of coral reefs a thousand or more feet above sea-level. In spite of these recent developments, the Wallace Line remains the structural division of the Asiatic from the Australasian portion of the region.

The climate is equatorial, but influenced by the monsoons. The temperature has the usual even record: e.g. Batavia has an annuai mean of 78° F. and a range of 2° F. The diurnal range is 5° F. But the winds are monsoonal and are controlled by the alternating high- and low-pressure centres in Asia and Australia. In July they blow from the south with an eastern component in the southern hemisphere and with a western component in the northern. In January these directions are reversed. Sea influence helps to steady the temperature, which is unusually equable. Owing to the high relief of the land, the rainfall is very heavy. The annual mean for the region as a whole is 100 inches, but among the hills of Java and the Philippines it rises to 250 or 300 inches. Baguio near Manila holds the world's record of 46 inches for precipitation during a single day. The weather hardly varies from day to day. The mornings are bright at first, but begin to cloud over by 9 o'clock. In the afternoon a heavy shower falls, after which the sky clears again. The nights are clear and windless.