1880.] On the Exploration of the Caves of Borneo. 317 



private enterprise, and that no further expense should be hazarded, 

 at any rate, until the higher parts of the island in the north-east may 

 be conveniently examined. 



A. HART EVERETT. 



John Evans, Esq. 



Sarawak, August 6th, 1879. 



Notes on the foregoing Report* 



Page 311. "Lines of old sea cliffs." — I inclose a rough sketch of the 

 Sibaiyat range of limestone hills, situated up the right-hand branch of 

 the Sarawak River, which will assist in giving an idea of the appear- 

 ance of the cliffs referred to. In the Staat Mountain similar cliffs 

 rise sheer up from the plain to a height of 1,200' feet. I also inclose 

 a sketch of that part of the Jambusan Hill known as Gunong Bak, in 

 which are found caves V, XIII, and XXI. This sketch was made about 

 three years after the jungle had been removed by a bush-fire, and it 

 will serve to show how the Sarawak limestone has been worn and 

 scarred by denudational agencies. 



Page 313. " Submerged to a depth of 500 feet." — I infer that the last 

 subsidence of north-west Borneo reached a depth of not less than 500 

 feet from the fact that the limestone hills between the upper part of the 

 Sarawak River and the Samarahan exhibit traces of marine denuda- 

 tion equally with the hills situated nearer to the coast, although their 

 bases are probably not less than 400 feet higher above the sea-level. 

 Pebbles of cinnabar ore have been met with on the summit of the 

 Busan Hills. The nearest deposit of cinnabar is that at Tagora, a 

 peak rising nearly 800 feet above the sea-level at the base of the 

 Bongoh Mountain, about eight miles to the southward. It can hardly 

 admit of doubt that these pebbles were carried to the spot in which 

 they occurred when the Busan Hills were submerged beneath the sea, 

 and, as the hills vary in height from 400 to 500 feet, we have, in this 

 instance, almost demonstrative evidence of subsidence to the depth 

 which I have indicated as a probable minimum. 



Page 313. " Indications of purely marine denudation." — Every lime- 

 stone hill is surrounded by a great assemblage of reefs, rocks, and sea- 

 stacks, which often extend from side to side of the smaller valleys. 

 Where the superficial alluvium has been removed, it is seen that these 

 rocks are, almost invariably, integral portions of a smoothly-worn and 

 hollowed floor of limestone. They decrease in number as the distance 

 from the hill is increased ; but, in the immediate vicinity, if the jungle 

 be cleared, the land may be observed to be literally studded with 

 masses of limestone, all fantastically worn, and varying from the 

 size of small boulders to that of craggy stacks, 30 or even 50 feet 

 high. Sometimes two reefs will run out parallel from the hill, and 



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