90 lEON OEE AND COAL DEPOSITS AT WAlLEEAWAfrG. 



Winter, of Wallerawang, who pointed it out to me, will be induced 

 to follow his discovery up. The narrowness of the opening is 

 not at all unfavourable to the supposition that the cave may 

 eventually prove to be an extensive one, for A'ery few limestone 

 caves present large and well-marked entrances. 



Caves in limestone have usually had their origin in fissures, 

 through which water flows or at one time flowed ; the water at 

 first slowly percolating through them, and then as the fissure 

 gradually became larger and larger tlie volume of water likewise 

 increased until the fissure became converted into a true under- 

 ground river or watercourse. Even in cases where no water flows 

 through them at the present day it can plainly be seen that such 

 was the case once, as exemplified in the caves or " swallow-holes" 

 of Yorkshire, the Katavothra of the Morea, South Australia, 

 and many other parts. 



These caves are eaten out of the limestone by the solvent power 

 which water charged with carbonic acid possesses. Ordinary water 

 free from carbonic acid would be quite incapable of dissolving out 

 the limestone, but all natural waters contain more or less of that 

 gas, derived by the rain from the atmosphere as it falls and from 

 the decaying vegetable matter which it meets with in its passage 

 through the soil. 



All limestone caves usually retain more or less completely 

 their original form of fissures, expanded, perhaps, in parts into 

 vast caves and chambers of immense proportions, but again 

 contracting a little further on into a mere crack or tunnel. 



Comparatively large rivers are received by such caves, which 

 then continue their course under ground, in some cases suddenly 

 appearing to the light of day again, but in others making their 

 way beneath the surface right out to sea. Certain of the South 

 Australian creeks are thus discharged. 



I do not refer to this subject of caves in limestone so much on 

 account of the supposed one at Wallerawang — for it may quite 

 likely be j^roved to be merely the beginning of one — as to draw 

 attention to the occiirreuce of such apertures in limestone dis- 

 tricts, in order that they may be properly investigated. 



In conclusion, I think I may safely say that this portion of the 

 district of Wallcrawang seems to be destined to be one of the 

 greatest and most flourishing portions of the Colony. Here, 

 within a comparatively small circle of some four miles diameter, 

 there are extensive and rich deposits of iron ores, coal, and 

 abundance of limestone. At present nothing beyond exploratory 

 work has been done with them ; but as the Wallerawang Iron and 

 Coal Company has taken up large selections of the lands for the 

 purpose of erecting iron works, there is a prospect that, in 

 a short time, an attempt may be made to utilize some of this 

 great wealth. 



