<;. T. PRIOlt. 
120 
(1) . Olivine-basalt, dill between the Gap and Horseshoe Bay (656). 
(2) . Hornblende-basalt, cone below Castle Hill (385). 
(3) . Hornblende-trachyte (trachydolerite), 500ft. up Observation Hill (277). 
(I). Phouolitie trachyte (trachydolerite), Scott Island. 
( 5 ) . Leucite-konyte, “ Keep” of Cape Royds, slope of Mount Erebus (818). 
(6) . Phonolitic trachyte, top of 900-ft. Knoll, Mount Terror (188). 
(7) . Phonolitic trachyte, crater of Brown Island (607). 
As an experiment in the use of the American quantitative system of classification* 
the “ norms ” (percentage mineral composition by weight) of the seven rocks were 
calculated, and are given in the following table : — 
G) 
(2) 
(3) 
(4) 
(5) 
(G) 
(7) 
KAlSi 3 0 8 
= 
10-55 
12-79 
28-95 
21-76 
22 - 92 
35-60 
29 ' 47 
NaAlSiA 
= 
4-19 
12-05 
29-30 
35-24 
41-47 
34-82 
39-30 
CiALSiA 
= 
20-57 
20-29 
4-69 
7-81 
12-23 
0-77 
2 • 50 
NaAlSiO., 
= 
12-78 
14-48 
21-56 
16-53 
11-07 
18-72 
23-66 
NaFcSiA 
= 
1-88 
1-58 
CaSiO s 
= 
11-71 
9-51 
5-23 
3-71 
0-46 
3-64 
1-62 
FeSi0 3 
= 
2-51 
2-90 
9-37 
0-39 
0-79 
MgSiOj 
= 
8-20 
6-00 
3-60 
1-30 
0-30 
0-66 
0-40 
Fc a Si0 4 
= 
3-67 
2-34 
3 " 67 
Mg.,Si0 4 
= 
10-78 
4-27 
1-96 
FeO ■ Fe A 
= 
4-17 
6-03 
2-25 
2-55 
2-32 
3-41 
1-39 
FeO • TiO a 
= 
9-27 
7-90 
2-54 
1-22 
2-28 
0-77 
O ' 16 
Ca 3 2P0 4 
= 
0-93 
1-55 
0-20 
0-31 
0-93 
The names which the rocks would receive in this new classification arc as follows 
(1) Limburgose. 
(2) Limburgose. 
(3) Laurdalose. 
(1) Esscxose. 
(5) Laurvikosc. 
(6) Miaskose. 
(7) Miaskose. 
The result shows that the classification supplies a variety of names to rocks not 
differing very widely in chemical composition. 
Another system for the chemical classification of igneous rocks, which has been 
recently brought forward, is that of Osann.f 
This classification is based on the molecular percentages as calculated from the 
results of analysis. For flic seven analyses the molecular percentages are as follows:— 
(i) 
(2) 
(3) 
0) 
(5) 
(6) 
(7) 
SiO., 
= 
45-06 
48-92 
62 • 78 
63-17 
63 " 66 
66-49 
66 • 92 
TiOj 
= 
3-96 
3-52 
1-13 
0-54 
1-05 
0-35 
0-20 
A1A 
9-44 
11-46 
13-81 
13-11 
13-96 
13-85 
15-14 
Fc.A 
— 
117 
1-72 
1-21 
0-75 
0-66 
1 • 49 
0-41 
FeO 
= 
8 * 73 
8-27 
1-79 
6-12 
8-71 
1 *37 
0-96 
CaO 
= 
11-87 
11-42 
4-18 
4-29 
3-89 
2-34 
1-58 
MgO 
— 
15-15 
8-15 
2 "42 
0-84 
2-14 
0-45 
0-27 
Na,0 
= 
3 • 40 
4-99 
9-17 
8-52 
8-09 
9-28 
10-89 
K..< ) 
= 
1-22 
1 • 55 
3-51 
2 • 66 
2-81 
4-38 
3-63 
* Quantitative Classification of Igneous Rocks, Cross, hidings, Pirsson and Washington, Chicago, 1903. 
t Osaun, Tsohonnak's Min. Petr. Mitth., 1900, Bd. xix, p. 351, and 1901, 13d, xx, p. 899, 
