236 COMPOSITION OF SOME PUMICE AND LAVA FROM THE PACIFIC. 
White pwmice.—Bondi beach, much waterworn. 
Chemical composition : 
Moisture ... res a wee oe a 1s 
Silica me eee 2. ries tee 68°149 
Alumin: oe oe Ms 16°493 
Tron venuioxide cae ah ae <a 200 
Iron monoxide ... ae ve es --» hone 
Mangane : eo PER 
Lime 4:005 
Magnesia none 
re a es ee ae POSS Sal 
Potash’. =, cee wy a re Paes ei! 8] 
99°447 
Sp. gr. 2107 at 18°C. in powder. 
I have not been able to analyse any of the specimens of pumice 
from the islands, so that no direct olay scans can hed de 
mens. Although the Bondi specimens were collected some years 
before the Krakatoa er uption of 1883, they may possibly have been 
drifted across from previous eruptions in that district. 
It would be very interesting to trace the limits of the distribu- 
tion of drift pumice along the Australian coast, and I trust that 
some one will undertake this dut ty. 
vd. sas wl oe from the island of Tanna, very 
vesioulay and almost a pumice in structure (See Rocks from New 
Britain and ee Trolend, A. Liversidge, F.R.S., Journ., Roy. 
Society, N.S.W., 188 2) 5 and in specific gravity it is just over 1°0, 
since it slowly sinks in water, but the powder has about the usual 
density of rocks. 
It also contains small white glassy crystals of felspar. This 
specimen was collected by the late Commodore Goodenough. 
Chemical composition : 
lg ips ra "201 
Sili su ais aay eh Me 57°041 
Alene re ik is --- 19°512 
Tron sesquioxide ... see aie aie -» 5°499 
ee monoxide eee ca bes bis, de 
: ssiaggeeaty monoxide ... ‘ 2-053 
me ie 8°157 
Magnesia . none 
Soda oy : ihe 2°831 
Potash . ‘ ‘ wet 2°37 
100°383 
Sp. gr. 2°720 at 212°C. in powder. 
—- 
fi ; : ny See ates 
kB ae a iS She yy a ek ae 
Asie 
ra 
2 z Spire gee GG 
Se aS RN tae Le SORTS ee eRe SIEGES eee ak Pen Be nen eR 
