THE ISLANDS AND THEIR POPULATION 29 
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affected by social causes which have not yet developed, 
the native population should attain twenty millions 
within forty years. In fact, it does not seem inconceiv- 
able that within a century the population may reach 
a hundred millions. 
This may appear an extravagant estimate; but it 
must be remembered that Java, an island not much 
larger than Luzon alone, now contains thirty million 
souls, or fifteen times as many as a hundred and forty 
years ago. Only a tenth of the area of the Philippines 
is at present under cultivation. There would therefore 
be room for a hundred million people to live with some 
comfort in the archipelago even without improvement in 
methods of agriculture. The subprovince of Ifugao, 
inhabited by the distinctly primitive tribe of the same 
name, is computed to contain 132,000 inhabitants 
with a total plane area of perhaps 750 square miles. The 
district is extremely rugged, and less than fifty square 
miles of it are actually cultivated, the lesser half of these 
being in rice. This means that more than two thousand 
people working with primitive tools derive their sub- 
sistence from each square mile cultivated. These truly 
astonishing conditions need only be appreciated to 
make almost any prophecy of the future populousness 
of the Philippines seem justifiable. 
With these half-tamed, head-hunting Ifugao living 
more than 170 to the square mile in their mountains, 
it is not surprising that certain of the civilized districts 
show an enormous congestion, far greater, in fact, than 
any parts of Europe but those industrially most active. 
Northern, central, and southern Luzon, as well as at 
least four of the central islands, contain tracts that 
sustain more than five hundred persons to the mile. 
In 1820, the ratio for the United States was five. The 
only portions of the Philippines that fall below this 
a 


