312 



THE ATLANTIC. 



[chap. v. 



and intermediate depths than in surface-water; but if regard 

 be had to the temperature of the water, it will be seen that 

 there is but little difference in the amount in waters of the 

 same temperature, from whatever depth they may have been 

 derived. This seems to indicate that the animal life at the 

 bottom and at great depths can not be very abundant, other- 

 wise there could hardly fail to be a decided excess of carbonic 

 acid in the deep water, owing to constant production and want 

 of the means of elimination of the gas. On this subject, howev- 

 er, it would be premature to speculate before the determination 

 of the oxygen, from which we may hope for much information. 



At a meeting of the Tloyal Society of Edinburgh, on the 4th 

 of June of the present year, Mr. Buchanan communicated the 

 results of an examination of the gases dissolved in sea-water at 

 different depths, esjoecially with reference to the amount of 

 oxygen contained. 



He finds that at the surface the amount of oxygen varies 

 between 33 and 35 per cent., the higher number having been 

 observed in a water collected almost on the Antarctic circle : 

 the smallest percentages have been observed in the trade-wind 

 districts. In bottom-water, the absolute amount is greatest in 

 Antarctic regions, diminishing generally toward the north. 

 The oxygen percentage is greatest over diatomaceous oozes, 

 and least over red clays containing peroxide of manganese : 

 over blue clays it is greater than over globigerina oozes. In 

 intermediate waters the remarkable fact was observed that the 

 oxygen diminishes down to a depth of 300 fathoms, at which 

 point it attains a minimum, after which the amount increases. 



The following figures show the nature of this phenomenon : 



Xature, July 26th, 1877. 



