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Lewy, have shown that the changes in the relative amounts 
of the several gases held in solution in sea- water depend : — 
(1) upon the variations in intensity of direct and diffused 
solar light, producing a corresponding effect upon the vitality 
of sea plants and animals ; and (2) upon the alterations in 
temperature affecting the relative amounts of the dissolved 
gases in accordance with the known laws of gaseous absorp- 
tion. Consequently if such cases can at all influence the 
composition of the atmosphere of the sea it is reasonable to 
expect that the variations would be most perceptible in the 
air above the tropical oceans, in whose tepid waters infusoria 
exist in enormous quantities, and where the intensity of total 
sunlight is very great and its changes exceedingly rapid. 
It would then appear from Lewy’s experiments that sea- 
air is sensibly richer in carbonic acid than the air of the 
land, and that, contrary to the a priori statements of Yogel 
and Kruger sea-water does not abstract the carbonic acid 
from the air, but even causes a sensible increase in its com- 
parative amount. Considering the difficulty generally ex- 
perienced in accurately noting in the eudiometer contractions 
so minute as the absorption of the carbonic acid from a 
small volume of atmospheric air, it appeared desirable to test 
the validity of the above conclusions by a series of experi- 
ments made by one of the more convenient and accurate 
methods which we now possess for the estimation of atmos- 
pheric carbonic acid. 
In a paper which had the honour of being read before the 
Society, the author communicated the results of a series of 
determinations of the amount of carbonic acid contained in 
the air over the Irish Sea. All these determinations were 
made by Peftenkofer’s method, according to which the 
amount of atmospheric carbonic acid can be estimated with 
far greater accuracy than by any eudiometric method 
hitherto described. The details of the method of analysis 
were fully described in the paper above referred to. The 
