GEOLOGICAL STRUCTURE. 415 



or alcove, with a brick floor and stone steps, and 

 wooden pillars and roof. From this there was a 

 fine view of the neighbourhood. It appeared that 

 the mass of hills I was upon was a continuation of 

 one of the ranges of Madura, having the same 

 height and general appearance. It is separated 

 from that island by the strait, and seems formerly 

 to have been itself an island, since it is everv 

 where surrounded by flat marshy land, and many 

 mangrove swamps. 



The hills are about three hundred and fifty feet 

 high, have an escarpment towards the north, and 

 the beds at the limestone caverns dip slightly south- 

 west. I found these caverns were artificial, being, 

 in fact, merely galleries formed by following along 

 the dip several beds of a white, soft, but gritty lime- 

 stone, which is found to make excellent drip-stones, 

 and has also been used for building. Some of the beds 

 had a concretionary structure ; others were made of 

 grains compacted together : both these resembled 

 beds which we had found on Raine's Islet. It ap- 

 pears to harden in the air, as, although many of the 

 beds were quite soft and friable in the roof and 

 sides of the caverns, parts of the same lying loose, as 

 well as fragments outside, and most of the weathered 

 surfaces were • hard, although very much corroded. 

 In some places there were cherty pieces quite smooth 

 and compact. Although I did not see any organic 

 remains of any kind, I have not the least doubt that 

 this limestone is the result of the detrition of corals, 



