5 
Deposits, Limestone Creek. 
the eastern bank of the creek the marble beds are capped by 
blue unaltered limestones containing fossils (molluscs). 
In ascending the steep and rugged ranges to the east, the 
porphyries become more compact and silicious, having a 
greyish or reddish felsitic base, with small translucent 
quartz-crystals, patches of pink-coloured felspar and 
fragments of other rocks, the whole Ibrming a breccia-like 
mass, as seen in specimen No. 6. On the summit of Mount 
Cobboras, and on the rocky-crested ridges near it, the rock 
masses weather into vertical layers with a northerly strike. 
Descending the eastern slopes of Mount Cobboras, the por- 
phyries previously described give place to salmon-coloured 
quartz-porphyries, almost granitic in structure and weather 
in rounded masses. 
EXAMINATION OP CAVES. 
Cave No. 1. — Pendergast’s Cave. 
The first examined is that perforating a marble deposit 
near the Limestone Hut (an out-station of Mr. James 
Pendergast, of Mount Leinster), For reference this may 
be called Pendergast’s Cave. In examining the ground plan 
of this cave (Diagram S), it will be seen that it traverses gener- 
ally the line of strike of the strata. This is the case with 
most of the caves examined, and would ajipear to indicate 
their origin to be by percolation of water from the adjoining 
ci'eeks. Wliat I mean by this is that the present water 
channel of the Limestone Creek, although in some cases at a 
lower level than the orifices forming the entrances to the 
caves, originally stood at a much higher level, and washed 
the bases of the limestone blufis ; then, percolating along the 
lines of strike, gradually eroded a channel to a lower level ; 
and, owing to the calcareous mass being traversed by joints 
and lines of shiinkage, the water charged with carbonic acid 
gradually decomposed the hard crystalline masses, and by 
the further mechanical action of silt and small stones eroded 
a larger passage. The action of rain water from above, 
acting similarly by its cai’bonic acid, derived from the decom- 
posing vegetable matter covering the calcareous deposits, 
would probably form many of the curiously-shaped holes 
and crevices seen on the surface.* 
* Vide Boyd Dawkins’ Cave Hunting, p. 53. 
