58G 



Dr. W. B. Carpenter on the 



[June 13, 



21, the Oxygen in bottom-w&ter did not average above 19*5 per cent., while 

 the Carbonic acid increased to nearly 28, — the percentage of Nitrogen 

 being reduced at the same time from 54 to 52*5. The percentage of Car- 

 bonic acid in bottom-water often rose much higher than this, being fre- 

 quently between 30 and 40, and in one instance more than 48 ; but the 

 percentage of Oxygen did not show a corresponding reduction, being never 

 less than 16, while that of Nitrogen came down from 54 to 34*5. Thus it 

 appeared that so long as Oxygen was present in sufficient proportion, the 

 increase of Carbonic acid to nearly half the total amount of the gases re- 

 movable by boiling did not exert any unfavourable influence on Animal 

 life ; from which it might be surmised that the Carbonic acid dissolved in 

 water under great pressure is in a condition altogether different from that 

 of gaseous Carbonic acid as regards its relation to Animal Respiration*. 



78. Having had an opportunity, in the ' Porcupine' Expedition of 1869, 

 of making myself acquainted with the method on which the Analyses of 

 the Gases of Sea- Water were conducted, and having provided myself on this 

 occasion with the requisite Apparatus, I believed myself able — though not 

 claiming to be an expert in Chemical Manipulation — to carry on similar 

 analyses with sufficient accuracy to determine whether the condition of the 

 abyssal water of the Mediterranean is really such as I had suspected it to 

 he. Each of the samples taken in the two deep Soundings (§ 72) was 

 boiled until no gas came over ; and the total quantity of gas given off, 

 which corresponded very closely with the average formerly obtained, was 

 divided in each case into two parts, so that I had four specimens in all. 

 The composition of these specimens agreed very closely ; the percentages 

 being approximately (for I do not pretend to minute accuracy) as follows : 

 Oxygen 5, Nitrogen 35, Carbonic acid 60. Thus it appeared that very 

 nearly the whole available Oxygen had been converted into Carbonic 

 acid ; so that while the proportion of Oxygen to Carbonic acid was never 

 in the open Ocean less than one third, it was here no more than one twelfth, 

 — a difference fully adequate to account for the paucity of Animal life on 

 the deep bottom of the Mediterranean. That this condition does not 

 extend to those moderate depths in which the water is subjected to the 

 disturbing action of winds, tides, and currents, may be fairly presumed : 

 but whether it prevails through the whole stratum beneath 250 or 300 

 fathoms, so as to constitute the essential condition by which Animal life is 

 limited to these depths, it would obviously be premature to assert. 



* It is by no means improbable that such sluggish animals as Mollusks and Echino- 

 derms may be able to bear a much larger proportion of Carbonic acid in the water they 

 breathe than Fishes and Crustacea. Experimental inquiries on this point, which might 

 be readily carried out in connexion with any large Aquarium, would give results of great 

 Physiological interest. 



