1890 - 91 .] Dr Murray and Mr Irvine on Silica in Seas. 
235 
silica necessary for their shells and skeletons these organisms must 
pass an enormous quantity of sea-water through their bodies. bTo 
interpretation like that adopted for the carbonate of lime organisms 
is possible here, for silica is present in solution in sea-water only in 
one condition, and our own and the analyses of different authorities 
give only the merest traces of soluble silica in sea-water. 
It will be seen, by reference to the accompanying Table, that the 
determinations of silica in sea-water by various authors can be 
Table I. — Silica in Various Sea Waters. 
Observer. 
Locality. 
Number of 
Determi- 
nations. 
Si0 2 in grms. 
per litre. 
Si0 2 in parts 
of Water. 
Max. 
1 Min. 
Max. 
Min. 
Forchammer, . . 
Atlantic, 
12 
0-1130 
1 0-0690 
9,090 
14,880 
Bibra, 
Do., 
2 
none 
Hunter, .... 
Do. (S.W. of Ire- 
land), . . 
t 13 
none 
Anderson (Gran- 
ton), 
Do., 
1 
0-0020 
513,500 
Do. Do., 
Do. (bottom water 
1760 fms.), 
1 
0-0040 
256,600 
Forchammer, . . 
Baltic Sea, .... 
2 
0-0720 
0-0270 
14,000 
37,260 
Sass, 
Do., .... 
[ 1 
0-0179 
56,200 
Gobel, jun., . . . 
Do., .... 
4 
0-0230 
0-0005 
43,740 
2,012,000 
C. Schmidt, . . . 
Do 
1 
0-0023 
437,400 
Do., . . . 
Coast of Norway, . . 
2 
0-0172 
0-0149 
60,000 
68,500 
Figuer and Mialhe, 
Havre, ...... 
1 
0-0085 
121,000 
Clemm, 
St George’s Channel, 
1 
trace 
Anderson (Gran- 
ton), 
North Sea, .... 
2 
0-0016 
0-0006 
640,000 
1,700,000 
Do. Do., . . 
Shore at Granton, . 
4 
o-ooio 
0-0003 
1,024,000 
3,410,000 
C. Schmidt, . . . 
Arctic Ocean, . . . 
1 
0-0144 
71,100 
Anderson, .... 
Mediterranean, . . ! 
1 
0-0074 
139,000 
Forchammer, . . 
West Mediterranean, 
4 
0-0870 
0-0800 
11,820 
12,900 
Do., . . 
Straits of Gibraltar, . 
2 
0-0930 
0-0730 
11,000 
14,000 
Do., . . 
At Malta, . . . . 
1 
0-0800 
12,900 
Do., . . 
East Mediterranean, 
5 
01380 
0-0290 
7,450 
35,500 
Vierthaler, . . . 
Adriatic, 
1 
o-noo 
9,340 
Rotmet and Lefort, 
Suez, ...... 
1 
trace 
C. Schmidt, . . . 
Red Sea, 
2 
0-0052 
0-0032 
197,700 
321,000 
Do., . . . 
Indian Ocean, . . . 
3 
0-0030 
0-0021 
342,300 
490,000 
Do., . . . 
South China Sea, . . 
1 
0-0032 
... 
321,000 
arranged into a maximum group, thirty in number, and a minimum 
group, twmnty-three in number. In the maximum group many of 
the determinations include phosphates along with silicic acid, and it 
appears evident, from our own analyses, as well as from the great 
irregularity of these maximum results, that the waters were not 
filtered before analysis — two samples of the same water from the 
Adriatic, for example, gave respectively 0T10 and 0‘237 grm. per 
litre. In the second or minimum group the waters have evidently 
been filtered before analysis, and the results exhibit a striking uni- 
