Various geomorphologists such as Bögli, Corbel and Lehmann have in recent years demonstrated the interest that certain simple chemical analyses of natural waters can have for the comparison of rates of limestone solution in different in different climatic conditions. They can also have their relevance for the tracing of underground water connections as Oertli (1953) has shown in the example of the Slovenian part of the classical Yugoslavian karst. Since 1957, the writer has therefore been making such analyses of waters from Australian limestone areas. The chief significance of these measurements comes when one caving area is compared with another. M.M. Sweeting (1960) has already commented briefly on observations from Mole Creek, Tasmania, Buchan, Victoria and the Fitzroy Basin, Western Australia, made in 1958-59 by herself and the writer; further discussion will appear in a forthcoming publication of ours on the Limestone Ranges of the Fitzroy Basin. Nevertheless measurements of this kind can have a certain intrinsic interest as it is hoped to show in the following notes on the few observations I made at Yarrangobilly. These observations are set out in tabular and Trombe graph forms; the locations of the collecting points are shown on the map.

River Cave is a Zwischenhohle (between-cave) in which the active river passage is reached through a former tributary stream passage from a dry valley. Now vadose in character, it is of gentle gradient, with some normally and some temporarily water-filled reaches of shallow phreatic nature. There is only a single level of development. Water tracing has confirmed previous inferences that it is mainly fed from the South Branch watersink, that its normal flow goes to the Blue Waterholes, the main rising of the Plain, and that there is flood overflow to Murray Cave, which is shown to have been formerly the normal outflow cave of the system. In the changeover from one outflow point (Vorfluter) to another, a shorter, steeper cave and longer surface course has been replaced by a longer cave of shorter gradient. Ev's Cave, a flood inflow cave of the South Branch, may also feed River Cave and Keith's Faint Cave is inferred to be part of the link between South Branch Sink and River Cave. It has the aspect of an early stage of vadose development from phreatic conditions. Previous interpretation of Glop Pot as a true phreatic relic is maintained in the light of new facts. Evidence is lacking with which to date the caves at all reliably. Glop Pot possibly belongs to a phase of surface planation of Tertiary age whereas the other caves are likely to be consequent on Pleistocene dissection. The tributary passage of River Cave and its associated dry valley may have lost their stream in the Holocene when Murray Cave became intermittent in action also. The Murray Cave event is due to subterranean piracy associated with rejuvenation whereas the loss of the tributary stream is probably in part due to increasing warmth and less effective precipitation.