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



313 



and subangular blocks of limestone. In cave No. V its summit is 

 nearly 50 feet above the floor of the cave. 



(3.) A stratum of river mud mingled with bat-guano, and witli 

 rounded masses of limestone and creamy crystalline stalagmite inter- 

 spersed. The maximum thickness observed in the excavations was 



3 feet. This stratum is crowded with the remains of bats, and also 

 with those of larger mammals — all (as I am led to understand) of 

 genera now extant in Borneo. The bones are almost invariably in a 

 very broken condition, and so rounded and water- worn as to be past 

 identification. As a sample of these bones has been examined in 

 England, it is not necessary to speak more particularly of them here. 

 In addition to the mammalian remains, the mud exhibits a miscel- 

 laneous assemblage of the remains of small reptiles (chiefly Chelonian), 

 fish bones and scales, chelae of crustaceans, land and fresh-water 

 shells, leaves, &c, &c. In the upper level of this river mud traces of 

 the presence of man are abundant, 



(4.) The yellow clay, more or less concreted into hard pseudo- 

 stalagmite, and containing casts of land shells, and bones and teeth of 

 pig. In No. XIII, a narrow band of nearly pure stalagmite (about 



4 inches thick) intervenes between the river mud and the yellow clay. 

 The latter deposit rests immediately on the limestone floor of the cave. 

 It contains a few water-worn pebbles and fine gravel, and it has been 

 extensively denuded, prior to the introduction of the river mud 

 above it. 



The foregoing series of deposits is found, with wonderfully slight 

 variation, at points so distant from each other as Jambnsan and Niah. 

 At both places the floors of the caves which present it are at a level of 

 some 40 feet above the flat land at the bases of the hills. All four 

 caves open on the face of a perpendicular cliff, so that their height 

 above the present valleys affords a gauge of the denudation of the soft 

 rocks in the vicinity of these hills since the introduction of the river 

 mud. 



The above are the principal kinds of deposits that are met with. 

 Apart from the evidence as to their slight antiquity afforded by the 

 mammalian remains, and by the fact of the presence of man in a fairly 

 advanced stage of civilisation in the particular instances examined, it 

 seems highly probable that the contents of all the Sarawak caves, at 

 least to a height of many hundred feet, will prove equally recent, and 

 for the following reason : The contents of the Sarawak caves must 

 have been accumulated since the date of the last submergence of 

 north-west Borneo, unless the subsidence of the land was very trifling 

 indeed. But the submergence actually went on to a depth of 500 

 feet, and probably much more, as is abundantly evidenced by the 

 indications of purely marine denudation on the inland hills ; and that 

 it was very recent in a geological sense may with fairness be deduced, 



