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 54*2, 

 carbon dioxide 20*7 ; this proportion was subject, 

 however, to great variations. Intermediate water 

 gave an average percentage of oxygen 22-0, nitrogen 

 528, and carbon dioxide 262 ; 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 : — 



T50 Fathoms, 



Oxygen 18-8 



Nitrogen .... 49-3 

 Carbon dioxide . . 31-9 



The greatly increased percentage of carbon dioxide 

 in the stratum of sea-water immediately overlying 



