498 THE DEPTHS OF THE SEA. (CHAP. X. 
permanganate test everywhere, and at all depths. 
The gas contained in the water was carefully ana- 
lysed, and it was found, as a general result, that 
the amount of free carbon dioxide increased and 
the proportion of oxygen diminished with increased 
depth. ‘There seemed to be reason to believe, how- 
ever, that the quantity of carbon dioxide depended 
to a great degree upon the abundance of the higher 
forms of life. Mr. Lant Carpenter used always to 
predict a bad haul for the zoologists when he found 
the proportion of carbon dioxide to the oxygen and 
nitrogen unusually low. ‘The great increase in the 
quantity of carbon dioxide was just above the bottom. 
The general average of thirty analyses of surface- 
water gives the following as the proportions of the 
contained gases present :—Oxygen 25:1, nitrogen 542, 
carbon dioxide 20°7; this proportion was subject, 
however, to great variations. Intermediate water 
gave an average percentage of oxygen 22°0, nitrogen 
52°8, and carbon dioxide 26:2; while bottom-waters 
gave—oxygen 19°5, nitrogen 52:6, and carbon dioxide 
27°9. But bottom-water, at a comparatively small 
depth, often contained as much carbon dioxide as 
intermediate water at much greater depths. In one 
of the serial soundings, in which the water was 
taken at every 50 fathoms, three analyses gave the 
following singular result :— 
750 fathoms. 800 fathoms. Bottom, 862 fathms. 
Oxygenye., fa). 26) 188 17°8 Lii-2 
Nitrogen, ifs. = 49:3 48°5 34°5 
Carbon dioxide . . 31:9 a3°7 48°3 
The greatly increased percentage of carbon dioxide 
in the stratum of sea-water immediately overlying 
