330 Correspondence. 
I have also a fossil Echinus from which the chalk has been entirely 
removed by acid, and on which the sulphate remains. beautifully 
arranged only around the lines of orifices between the plates. 
‘May I presume to draw the inference that the above facts lend 
confirmation to Dr. Bowerbank’s views on the spongeous basis of 
many flints? May they not also be adduced in support of the opinion 
that holds the animal nature of sponges? We know that animal 
substances are partly albuminous, and that sulphur is one of the 
elements of albumen. The animal substance, in undergoing decom- 
position, during or previous to fossilization, would part with its 
sulphur, which would be seized by the lime of the chalk in imme- 
diate contact with it, and hence the coating of sulphate of lime, for 
which I was totally unable to account, until Dr. Bowerbank was 
kind enough to impart to me some of the vast information he has 
amassed on the nature and habits of sponges, recent and fossil.’ 
I feel it to be due to your readers te state, that Ihave since found 
that there was a great mistake in my experiments, and that the inso- 
luble substance left on the flint after the solution of the chalk by 
hydrochloric acid was not a sulphate of lime, but simply a modi- 
fication of silica (the base of flints).. With the supposed fact fall, of 
course, the inferences which seemed to lend support to views that 
doubtless stand in small need to be propped up by error. Had I 
been more thorough in experimental chemistry, I should not have 
made this blunder; had I been wiser, I should not have ventured 
‘beyond my Jast.’—I remain, &c, W. B. Kestevan, F.R.C.S. 
Urrrr Hotroway, Lonpon. 
MISCELUIUANEOUS. 
— > 
ALLEGED GOLD-FIELD AT THE HEAD oF THE NEPEAN River, 
New Sourn Wates. By the Rev. W. B. Crarxe, F.G.S., &c. 
(Extracted from a Letter to the Editor of the Sydney Herald.)— - 
The eastern boundary of the plateau in which the Macquarie 
and the Nepean rise is the escarpment which backs the Illawarra, 
where it is about 2,000 feet above the sea, and the Nepean 
waters falling westerly from the edge collect in a channel which 
runs to the northward, other branches falling from the northern 
slope of the Mittagong more to the westward, towards the road to 
Bong Bong, and not far from where it leaves the Berrima road at 
Little Forest. 
The Cordeaux River collects in numerous heads along the edge of 
the escarpment farther to the north, and the back of Mount Kembla, 
and finally it joins the Nepean at the Pheasant’s Nest. At one spot 
Nepean waters collect behind a ridge, not more than fifteen chains 
distant from the swamps of the Cordeaux. Intermediately, a Nepean 
water rises near Geringulli Mountain, where the elevation is about 
1,800 feet above the sea, and runs at first northerly, and then turns 
to the west to join the main stream. The whole extent of the coast- 
