bo 
eo 
Or 
On the Composition of some Pumice and Lava 
from the Pacific. 
By A. Liversiper, F.R.S., Professor of Chemistry in the 
University of Sydney. 
[Read before the Royal Society of N.S.W., 1 December, 1886.] 
Bonn. 
Pumice.—Masses of pumice are frequently cast upon the beach 
along the coast of New South Wales, and at times are also 
found in the harbours, and they are not unfrequently picked up 
within the Sydney harbour. 
€ source of this pumice is, of course, a foreign one, and 
doubtless it is derived from more than one of the volcanic centres 
in the Pacific, but which of them does not as yet appear to be 
very clear. 
It is stated to be more abundant after an easterly gale, and is 
found more often on the north side of the inlets along the coast 
than in other situations ; in size the pieces vary from quite small 
fragments to pieces 9 or 12 inches through. 
Some of the specimens are black and others are white, or rather 
of a dirty white or grey colour. 
Thinking that the chemical composition might throw some light 
on their source, analyses were made of a specimen of each variety 
with the following results :— 
Black pwmice.—Bondi beach. 
Chemical composition : 
Moisture: ... 147 
Silica 3°630 
Tron sesquioxide ... pe ise ro ~. $838 
Tron monoxide ... sey ue Fe ... traces 
an monoxide ae 
en ¢ 4°205 
esia . none 
ny 4°252 
Potash : 3°809 
100°566 
Sp. gr. 2°307 at 15°C. in powder. 
