EXPLORATION OF THE CAVES OF EORNEO. .2/0 



The limestone lulls nowhere attain to a greater elevation than 

 1,S00 feet above the sea-level, at any rate in Sarawak, and they 

 more commonly vary from 30 J feet to 80 ) feet in height. In the 

 Baram district, the Molu Mountain is said to be limestone and to 

 rise to a height of 9,00J feet, but I am not aware that it has ever 

 been visited by a European observer. The hills invariably spring- 

 up steeply from the low country, and the majority of them present 

 lines of old sea-cliffs which generally face to N. and N.W., i.e., 

 towards the quarter still occupied by the waters of the sea. The 

 rock itself is much fissured and jointed, and the hills, in many 

 instances, are absolutely honeycombed with caverns. 



As is usual in limestone districts, the drainage of the country 

 is largely subterranean. Owing to this fact, coupled with the 

 heavy rainfall (the mean for the last three years was 135 inches 

 at K.uching), the land at the base of the hills is subject to fre- 

 quent flooding during the prevalence of the north-east monsoon, 

 when the underground watercourses are of insufficient capacity to 

 carry off the water as fast as it reaches them. As an instance of 

 the extent to which subterraneous drainage with its consequent 

 subterranean denudation has gone on in Sarawak, I may cite the 

 Siniawan river, which passes beneath four distinct hills in its short 

 course, and one of these hills — the Janibusan Hill — is pierced 

 "besides by at least three ancient river-tunnels of large size at vary- 

 ing levels. 



2. The Cares an (J tJteir Deposits. 



The total number of the caves examined by me has been 

 thirty-two, of which two were situated in Mount Solus, up the 

 Niah river, and the remainder in Upper Sarawak Proper. They 

 comprised examples of tunnel, fissure, and ordinary ramifying 

 caverns. Partial excavations were carried on in twelve of these 

 caves. The deposits contained in them varied. A few afforded 

 nothing but thick accumulations of bats' or bird-guano still in 

 process of deposition. This deposit was examined in three in- 

 stances, and proved to be perfectly barren, with the exception of 

 a few of the bones of the bats and swifts, to which it owed its 

 production. The commonest deposit in the caves of Upper Sarawak 

 was found to be an exceedingly tenacious, dark yellow, homo- 

 geneous clay, which is sometimes crusted over with as much as a 



