276 
ANALYSES OF ROCKS, TJ. S. GEOLOGICAL SURVEY. 
[no. 228. 
TASMANIA. 
Two analyses of so-called ''volcanic bombs" or "buttons" were 
made by W. F. Hillebrand, record No. 2007, at the request of W. H| 
Twelvetrees, of Launceston, Tasmania. These curious forms of vol! 
canic glass have every appearance of artificiality, but are said to be 
found under conditions and in so many localities that the idea of their 
human origin is precluded. A paper on the subject by R. H. Walcott 
may be found in Proc. Roy. Soc. Victoria, vol. 11, p. 23, 1898. 
A. From Upper Weld tindrift. Almerose. Analysis incomplete 
because of insufficient material. Sp. gr., 2.454 at 18.5°. 
B. From Pieman. I. 3. £ 3. Sp. gr., 2.428 at 22°. 
A. 
B. 
Si0 2 • 
69.80 
15. 02 
.40 
4.65 
2.47 
3.20 
1.29 
2.56 
undet. 
undet. 
.80 
(?) 
.18 
(?) 
(?) 
none 
none 
trace 
73. 59 
12.35 
. 38 
3. 79 
1.80 
3,76 
1.03 | 
1.93 ' 
.27 , 
.53 
.70 
.01 
.15 
nonl ; 
trace? 
trace 
trace 
trace 
ALO, 
Fe,0, 
FeO , . , 
MgO , 
CaO 
Na,0 
K 2 
H 2 at 105° 
H 2 above 105° 
Ti0 2 
ZrO , 
MnO 
NiO 
CuO 
SrO 
BaO 
Li 2 
100. 37 
100. 29" | 
1 
