NOTE ON LIMESTONE OCCURRING NEAR SYDNEY. 303 
very small quantities ; they contain a large quantity of carbonate 
of iron, and the clay appears to be the same as that contained in 
the limestone. Time did not permit a quantitative analysis to be 
made of these nodules, and other material, but I hope to complete 
this later. I was informed that under these nodules the lime- 
stone continues, but I was unable to ascertain the fact, as itis the 
bed of the creek where the quarry is situated. If this is so, 
probably it is a fissure filled with the material. The fissures 
filled with clay, found in the Hawkesbury Sandstones, (one of which 
has been opened out at Kogarah to a good depth, and the whole 
width) contain clay of a very good quality, and which consistently 
shows absence of lime, with but a trace of magnesia. Now the 
clay left on removing the substances soluble in hydrochloric acid 
from the limestone, is qualitatively identical with that of Kogarah 
and other like deposits, lime being absent, but a trace of iron, and 
a small quantity of magnesia, in fact, almost pure silicate of 
alumina. 
Favouring this idea of a fissure, is, that at the locality near 
Homebush, where I obtained a specimen of limestone almost 
identical with that from Duck Creek, the material has been 
quarried for a good distance along what appears to have been a 
fissure, and used for road making. This locality is perhaps two 
miles distant from Duck Creek at Auburn. 
The following is an analysis of the limestone from Duck Creek: 
C2 C07 aoe , ... 39°673 per cent. 
Clay = a a ms Ben ELS . 
Fe, 0. .— ms neh Bit ba POSE if 
Be CO ia... vn ee a L3480 ‘. 
Mn CO; = @... ae Kf sb aD) fd 
MeO ao. a bibs Pe eo aM 
Alkalies present as chlorides = shy Oso Kes 
Water = ésfe - wy SUMO és 
100-244 
