EEPORT ON THE DEEP-SEA DEPOSITS. 
457 
The results of the (rough) proximate analyses were as follows : — 
Found in 100 parts of 
Moisture (100°), • • . . 
Part decomposible by hot hydrochloric acid,i 
Part decomposible by hot vitriol, , , 
Ultimate residue, .... 
• 
• 
Keal Pumice. 
. 1-0 
6-9 
5-1 
87-0 
Qua.si-Pumice. 
13-5 
34-0 
44-5 
8-0 
100-0 
100-0 
The ultimate residues were ignited before being weighed and they were analysed in that condition, which, 
as it now strikes me, may perhaps have been a mistake ; but if so it cannot now be rectified. The results 
of the analyses were as follows : — 
Found in 100 parts oi purified 
Pumice. 
Quasi-Pumice. 
Silica, ..... 
76-41 
56-77 
Alumina (including trace of Fe 203 ), 
15-53 
25-21 
Lime, . . . . 
. ■ 2-11 
9-09 
Magnesia, ..... 
0-40 
1-37 
Potash, ..... 
2-26 
3-36 
Soda, ..... 
2-98 
4-19 
Moisture,- ..... 
0-20 
1-11 
99-89 
101-10 
Co nverting these numbers into multiples of SiOg, 
AI 2 O 3 , &c., we have for the 
Eeal Pumice. 
Quasi. 
SiOa 
1 
1 
AI 2 O 3 , ..... 
. 0-1186 
0-2592 
(or ^ AI 2 O 3 ), .... 
. (0-3558) 
(0-7776) 
CaO, 
. 0-0296 
0-1716 
MgO, 
. 0-0079 
0-0362 
KoO, ... 
. 0-0189 
0-0378 
Na^O, . . . . . 
. 0-0377 
0-0714 
or,'' taking EO as a general symbol for E"0, JAI 2 O 3 , 
E' 20 , we have in 
multiples of 
SiOa 
EO 
Eeal Pumice, .... 
1 
0-4499 
Quasi, . .... 
1 
1-0946 
or, separating the bases into EgOg ’s and EO ’s (where EO = CaO, KgO 
&c.) 
SiOj 
E 2 O 3 
EO 
Eeal Pumice, .... 
10 
1-19 
1 (-0-06) 
Quasi, , . . . . 
4 
1-037 
1-27 
Eammesberg, in his Dictionary of Chemical Mineralogy (quoting from an extensive research by Abich) gives a 
number of analyses by that chemist, from which it appears that pumices and obsidians (which, with him, are only 
two forms of the same genus) arrange themselves into two sets — A and B. 
The 
in A are, 
in B are, 
Orthoclase and albite, 
General symbols, 
(SiOals (E203 )s (RO)s 
4 ’5 to 5‘5 1 1 
6-5 to 8-5 1 
6 1 1 
n m 2> 
1 By difference ; includes combined HoO. ^ Absorbed during preservation in tubes. 
(deep-sea deposits chall. exp. — 1891.) 
60 
