1869.] on the Scientific Exploration of the Deep Sea. 479 



bearing. — The general average of thirty analyses of surface~vr&ter gives the 

 following as the percentage proportions : — 25*1 Oxygen, 54*2 Nitrogen, 20*7 

 Carbonic Acid. This proportion, however, was subject to great variations, 

 as will be presently shown. As a general rule, the proportion of Oxygen 

 was found to diminish, and that of Carbonic Acid to increase, with the 

 depth, the results of analyses of intermediate waters giving a percentage 

 of 22'0 Oxygen, 52*8 Nitrogen, and 26*2 Carbonic Acid; whilst the re- 

 sults of analyses of bottom-waters gave 19*5 Oxygen, 52'6 Nitrogen, and 

 27* 9 Carbonic Acid. But bottom- water at a comparatively small depth 

 often contained as much Carbonic Acid and as little Oxygen as interme- 

 diate water at much greater depths ; and the proportion of Carbonic Acid 

 to Oxygen in bottoin-wattx was found to bear a much closer relation to the 

 abundance of Animal life (especially of the more elevated types), as shown 

 by the Dredge, than to its depth. This was very strikingly shown in an 

 instance in which analyses were made of the gases contained in samples of 

 water collected at every 50 fathoms, from 400 fathoms to the bottom at 

 862 fathoms, the percentage results being as follows 



750 fath. 800 fath. Bottom, 862 fath. 



Oxygen 18*8 178 17'2 



Nitrogen 49*3 48*5 34'5 



Carbonic Acid. . . . 31-9 337 48-3 



The extraordinarily augmented percentage of Carbonic Acid in the 

 stratum of water here immediately overlying the Sea-bed was accompanied 

 by a great abundance of Animal life. On the other hand, the lowest per- 

 centage of Carbonic Acid found in bottom-water (viz. 7'9) was accompanied 

 by a "very bad haul." In several cases in which the depths were nearly 

 the same, the analyst ventured a prediction as to the abundance, or other- 

 wise, of Animal life, from the proportion of Carbonic Acid in the bottom - 

 water ; and his prediction proved in every instance correct. 



131. It would appear probable, therefore, that the increase in the pro- 

 portion of Carbonic Acid, and the diminution in that of the Oxygen, in the 

 abyssal waters of the Ocean, is due to the Respiratory process ; which is no 

 less a necessary condition of the existence of Animal life on the sea-bed 

 than is the presence of food-material for its sustenance. And it is further 

 obvious that the continued consumption of Oxygen and liberation of Car- 

 bonic Acid would soon render the stratum of water immediately above the 

 bottom completely irrespirable (in the absence of any antagonistic process 

 of Vegetation) were it not for the upward diffusion of the Carbonic Acid 

 through the intermediate waters to the surface, and the downward diffusion 

 of Oxygen from the surface to the depths below. A continual interchange 

 will take place at the surface between the gases of the Sea-water and those 

 of the Atmosphere ; and thus the Respiration of the Abyssal Fauna is pro- 

 vided for by a process of diffusion, which may have to operate through three 

 miles or more of intervening water. 



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