984 
THE VOYAGE OF H.M.S. CHALLENGER, 
into its partial pressure in the undissolved residue, and as the coefficient of absorption 
of oxygen is greater than that of nitrogen, the percentage of oxygen in the dissolved air 
is greater, and that in the undissolved residue is less, than that prevailing in the natural 
air. The ratio of the two percentages obviously depends on the relative volume of ab- 
used, but we need not trouble ourselves with the somewhat complex general formula, 
because for our purpose it is sufficient to consider the special case which applies to the 
ocean surface, and which presents itself when the shaking is repeated with constantly 
renewed air until the last instalment of air remains unchanged. In this case (which 
for us is the general case) the volume of air dissolved at a given temperature t by 
one litre of sea water is a quantity X, which is a function only of t and the pressure 
of the atmosphere, and every c.c. of dissolved gas contains nj c.c. of oxygen and 
n 2 c.c. of nitrogen, where ni and n 2 depend only on t, but change very slowly with the 
latter. 
“ According to my own determinations, as fully reported in the Memoir, 
“ One litre of Sea Water when saturated ivith { constantly renewed) air at t° and a pressure 
of 7 6 0 mm. {plus the tension of vapour of 'water at t°) takes up the following 
volumes {measured dry at 0° and 760 mm. pressure ) of the two gases : — 
Temperature, 
Centigrade. 
Dissolved Nitrogen and Oxygen in Cubic Centimetres. 
Percentage of Oxygen in 
dissolved Gas. 
N itrogen. 
Oxygen. 
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 
i 
i 
8-36 
4T7 
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*6 and 33 '2 mm. respectively. Now the sea, as far as 
