350 
ISLAND LIFE. 
[part ii. 
from a continent, yet separated from it by so shallow a sea. 
Becent changes of sea and land must have occurred here on a 
grand scale, and this adds to the interest attaching to the study 
of this large island. 
The internal geography of Borneo is somewhat peculiar. A 
large portion of its surface is lowland, consisting of great alluvial 
valleys which penetrate far into the interior ; while the moun- 
tains except in the north, are of no great elevation, and there 
are no extensive plateaux. A subsidence of 500 feet would allow 
the sea to fill the great valleys of the Pontianak, Banjarmassing, 
and Coti rivers, almost to the centre of the island, greatly reducing 
its extent, and causing it to resemble in form the island of Celebes 
to the east of it. 
In geological structure Borneo is thoroughly continental, 
possessing formations of all ages, with basalt and crystalline 
rocks, but no recent volcanoes. It possesses vast beds of coal of 
Tertiary age ; and these, no less than the great extent of alluvial 
deposits in its valleys, indicate great changes of level in recent 
geological times. 
Having thus briefly indicated those physical features of Borneo 
which are necessary for our inquiry, let us turn to the organic 
world. 
Neither as regards this great island nor those which surround 
it, have we the amount of detailed information in a convenient 
form that is required for a full elucidation of its past history* 
We have, however, a tolerable acquaintance with the two higher 
groups — mammalia and birds, both of Borneo and of all the 
surrounding countries, and to these alone will it be necessary to 
refer in any detail. The most convenient course, and that which 
will make the subject easiest for the reader, will be to give, 
first, a connected sketch of what is known of the zoology of 
Borneo itself, with the main conclusions to which they point ; and 
then to discuss the mutual relations of some of the adjacent 
islands, and the series of geographical changes that seem required 
to explain them. 
