PHOSPHATIC DEPOSITS IN THE JENOLAN CAVES. 331 
(6.) Nodular, greyish-coloured substance, found in the Imperial 
Cave. 
Analysis. 
Moisture at 100° C. a aie 6:79 
Combined water... ae J 3°52 
Silica (Si0,)... Me, ane see 54:13 
Alumina (Al,0;)_... es ae LdavS 
Ferric oxide FeO)... aon Aa. 7°46 
Lime (CaQ)... eat an ws» |. absent; 
Magnesia (MgO)... ree ... minute trace. 
Potash (K.O) sae Bis bs 1:69 
Soda (Na,0)... ane sie ST 
Phosphoric acid (P, O. By) hie: Os 10°63 
100-22 
(7.) White saline substance, exuding from crevices in the 
Devil’s Coach-house. A qualitative analysis proved this salt to 
be nitre (potassic nitrate). A small quantity of lime, magnesia, 
chlorine, and sulphuric acid was detected. The author suggests 
that the phosphatic deposits were due, in the first case, to sedi- 
mentary silt, containing bones derived from the remains of animals, 
brought to their present location by an ancient river. The presence 
of large quantities of drift, fine river wash, red and white marls, in 
and above the caves, all tend to point in this direction. 
The present deposits are of a secondary formation, due to the 
action of acidulated waters containing carbonic, organic acids, &ce., 
which have percolated through the primary deposits of drift, silt, 
&c., thereby dissolving the bone material, and acting on the marls 
dissolved a portion of the alumina and potash, the solution con- 
taining the phosphates having been re-deposited under conditions 
favourable for their separation. 
The origin of the deposits, however, and the conditions under 
which they have been redeposited is exceedingly interesting, and 
is open to wide discussion. 
With regard to the extent of the deposits, it is impossible at 
present to form any opinion, owing to the difficulty of access to the 
Caves. It is probable, however, that the supply is very limited. 
My thanks are due to Mr. Harpur, Assistant Curator to the 
Geological Survey Branch, for the second collection of phosphatic 
deposits exhibited at this meeting, also for notes made during his 
recent visit to the Caves. 
The analysis of No. 2 was kindly made for me by Mr. H. P. 
White, Assistant Analyst in the Laboratory. 
