328 PROCEEDINGS OF SECTION B. 
Geology.—Professor David, B.A., F.G.8., states, with regard to 
the geology of the caves district :—‘ The caves, which are large 
and very numerous, occur in a thick bed of limestone. The lime- 
stone is formed largely by corals, hydro-corallines (stromatorella 
being very abundant), and brachiopods ; amongst the latter a large 
pentamerus predominates. The limestone is considered by R. 
Etheridge, jun., to be of Siluro-Devonian age. It is interstratified 
with a thick series of blackish, greenish, grey, and reddish brown 
clay shales, claystones, and cherts, these containing casts of 
radiolaria. ‘The whole of the sedimentary series are intruded by 
quartz felsites and basic dykes rich in augite.” Mr. Harpur, 
Assistant Curator to the Department of Mines, who recently 
visited the caves, informs me :—‘“ A quantity of drift is associated 
with or immediately overlies the red and white marls which partly 
fill portions of the caves. The marls appear to graduate down- 
wards, and are red and white in colour.” 
A sample of the reddish marl taken from the Derails Coachhouse 
yielded on analysis as follows :— 
Analysis. 
Hygroscopic moisture... ae Nees 5 1:49 
Combined water ... Be an a veo, oO 
Silica (SiO,) ase ey Qos. Aas ave ~Od-4sll 
Alumina (A1,0)... = he ee wun, S502 
Ferric oxide (Fe,O,) ae ae as won RES 
Manganous oxide (MnO) fs: me ... trace. 
Lime (CaO) hts ar a re es, 16 
Magnesia (MgO)... ae aoe Bee wise “79 
Potash (K,O a es wae oe =. —oc09 
Soda (Na,O) ye a Ny eons ... tYace. 
Phosphoric acid (P,O;) ... roe ak 8 ‘08 
Organic matter ... Be ee aa a8 24 
99°62 
(1 and 2.) Light, porous, friable substance, white in colour ; 
soluble in dilute muriatic acid. Found in Katie’s Bower, Left 
Imperial Cave. 
This deposit occurs in veins in the marls. ‘The presence of a 
large quantity of red clay is very noticable in this cave ; in fact, it 
forms a boundary at one end of the earth deposit. The clay is also 
present in the ‘“‘ wash,” being possibly the fine sediment deposited 
in the side channels and quiet pools of a one-time underground 
river. 
