218 
COMPENDIUM OF GEOGRAPHY AND TRAVEL 
interior. In the beginning of the Diluvial period these 
gulfs began slowly to give place to dry land ; a strip of 
flat land was formed along the foot of the mountains, and 
gold, diamonds, and platinum, swept down by running 
water, were here deposited. The seas became shallower 
and retreated, and the present period commenced.” 
From the above sketch, the general configuration of 
Borneo of the present time can be gathered. We find a 
skeleton mountain formation in which the mountains, 
although arranged in chains, are not continuously elevated, 
but more or less separate and insular in nature; a hill- 
land of Tertiary age surrounding it, and in turn bordered 
by a dry plain land, which merges imperceptibly into 
vast swamps and morasses, through w T hich large and tor¬ 
tuous rivers find their way to a shallow sea. This rough 
outline does not, of course, hold equally good for all 
localities. Thus in British North Borneo the land is 
more elevated, and the older rocks in close approxima¬ 
tion to the sea, and the formation in Brunei and in the 
western promontory of the island is likewise irregular. 
It is in the southern and eastern portions that the char¬ 
acters mentioned are most apparent. Here we have four 
main basins, drained principally by the Kapuas, Barito, 
Koti, and Kayan rivers, and separated from each other 
by mountain chains. 
The Tertiary beds of which the hill and lower lands 
are composed have been separated into Eocene, Oligocene, 
and Miocene. Dr. Posewitz states that “ all four stages 
of the Eocene are developed in Borneo. The first or 
breccia stage, consisting of conglomerates and sandstones, 
is up to the present only known in West Borneo. The 
second, or sandstone stage, is of great thickness and wide 
development; it yields the Indian coal, and consists of 
quartz, sandstones, shales, and coal seams. The third, or 
