GEOGRAPHY OF BORNEO 3 



of the alluvium brought down by the many rivers 

 from the central highlands. This belt of alluvium 

 extends inland in many parts for fifty miles or more, 

 and is especially extensive in the south and south- 

 east of the island. 



Between the swampy coast belt and the mountains 

 intervenes a zone of very irregular hill country, of 

 which the average height above the sea- level is 

 about one thousand feet, with occasional peaks rising 

 to five or six thousand feet or more. 



There seems good reason to believe that at a 

 comparatively recent date Borneo was continuous 

 with the mainland of Asia, forming its south-eastern 

 extremity. Together with Sumatra and Java it 

 stands upon a submarine bank, which is nowhere 

 more than one hundred fathoms below the surface, 

 but which plunges down to a much greater depth 

 along a line a little east of Borneo (Wallace's line). 

 The abundance of volcanic activity in the archi- 

 pelago marks it as a part of the earth's crust liable to 

 changes of elevation, and the accumulation of volcanic 

 matter would tend to make it an area of subsidence ; 

 while the north-east monsoon, which blows with 

 considerable violence down the China Sea for about 

 four months of each year, may have hastened the 

 separation of Borneo from the mainland. That this 

 separation was effected in a very recent geological 

 period is shown by the presence in Borneo of many 

 species of Asiatic mammals both large and small, 

 notably the rhinoceros {R. borniensis, closely allied 

 to R. sumatranus) ; the elephant {^E. indicus, which, 

 however, may have been imported by man); the wild 

 cattle {Bos sondiacuSy which occurs also in Sumatra) ; 

 several species of deer and pig (some of which are 

 found in Sumatra and the mainland); several species 

 of the cat tribe, of which the tiger-cat {Felts nebulosa) 

 is the largest ; the civet-cat ( Viverrd) and its con- 

 geners Hemigale, Paradoxurus, and Arctogale ; the 



