The unhealthiness of the city is chiefly due to want of proper drainage, impure drinkingwater, miasma from the disturbed rubbish heaps, and contaminated dust from the uncleansed roads and streets.
Mangrove swamps surround the town and epidemics of cholera, yellow fever and other tropical diseases have been frequent; but the unhealthiness of the climate is mitigated to some extent by the high tides which cover the marshes, and the invigorating breezes which blow in from the sea.
The unhealthiness of certain portions of the county caused by the marshes is practically removed by draining.
In 1699 Batavia was visited by a terrible earthquake, and the streams were choked by the mud from the volcano of Gunong Salak; they overflowed the surrounding country and made it a swamp, by which the climate was so affected that the city became notorious for its unhealthiness, and was in great danger of being altogether abandoned.
The great fertility of these regions and the marvellous wealth of their forests are irresistible attractions to industrial and commercial enterprise, but their unhealthiness restricts development and is a bar to any satisfactory increase in population.