224 
THE VOYAGE OF H.M.S. CHALLENGER. 
One litre of Sear Water when saturated with {constantly renewed) air at t° and a 'pressure 
of (7G0 mm. plus the tension of vapour of water at t°) takes up the following 
volumes {measured dry at 0° and 7G0 mm. pressure) of the two gases : — 
Temperature. 
Dissolved Nitrogen and Oxygen in Cubic Centimetres. 
Percentage of Oxygen in 
Centigrade. 
Nitrogen. 
Oxygen. 
dissolved Gas. 
0° 
15-60 
8-18 
34-40 
5° 
13-86 
7-22 
34-24 
10° 
12-47 
6-45 
34-09 
15° 
11-34 
5-83 
33-93 
20° 
10-41 
5-31 
33-78 
25° 
9-62 
4-87 
33-62 
30° 
8-94 
4-50 
33-47 
35° 
8-36 
417 
33-31 
The temperature of the surface water of the ocean never falls very far below 0 ° C., 
even in the polar regions (the Challenger registered 27° F in the Antarctic ocean), 
while even in the tropics it rarely rises above 30° C. The corresponding tensions 
of aqueous vapour are 4'G and 332 millimetres respectively. Now the sea, as far as 
we know, derives all its absorbed oxygen and nitrogen from the atmosphere, — 
neither gas can come in from any other source, apart perhaps from a small quantity of 
nitrogen produced in the putrefaction of the bodies of marine animals and plants, which 
may, however, be safely neglected. Hence, we should say the ocean can nowhere contain 
more than 1 5*G c.c. of nitrogen and 8*18 c.c. of oxygen gas per litre, and the quantity of 
tj Q 
nitrogen per litre will never fall below — 7^0 x8'94 = 8'55 c.c. We cannot make a 
-imilar assertion in regard to the oxygen, and for it put down the minimum at 
727 
n x 4 50 = 4'30 c.c., because it is liable to constant diminution by the processes of life and 
putrefaction and processes of oxidation generally. 
At any point in the surface of the ocean the air dissolved in the water constantly 
t- mb to assume the composition demanded for the prevailing temperature by the 
a'>«orptiometric equations which served to calculate our table. But it is rarely possible 
f r it to assume this composition. Because, the water being in a continual state of 
pr*.-r< ssivc motion constantly flows from one set of conditions into others. And sup- 
i" m ~ < vi n a certain area of the ocean surface were in a state of stagnation, the 
