282 EXPLORATION OF THE CAVES OF BORNEO. 



NOTES ON THE FOREGOING REPORT, 



Page 278.—" Submerged to a depth ofoQOfret"—! 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 denudation 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 278. — " Indications of purely marine denudation.'" — Every 

 limestone hill is surrounded by a great assemblage of reefs, rocks, 

 and sea-stacks, which often extend from side to side of the smaller 

 vallej^s. "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 laud may be ob- 

 served to be literally studded with masses of limestone, all fantas- 

 tically 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 form a miniature cove, 

 with a small cave at its inland extremity. The most striking 

 form presented by the rocks are those of the " tabular " and 

 " mushroom " types. Their bases being protected from the honey- 



