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Livrs & Bhaxu—The Carbonic Anhydride of the Atmosphere. 181 
way or the other, to be arrived at. As the question is both in- 
teresting and important it is to be hoped that it will be further 
investigated, and will not be lost sight of by future scientific expe- 
ditions, asit has been by the past, with the solitary exception, we 
believe, of the French Transit of Venus expedition. 
Day and Night. 
As plants decompose carbonic anhydride only in presence of 
sunlight, it was to be anticipated that in the air over land surfaces 
there would be a diminution in the amount of that gas during day 
time, and an increase in the night. That such variations do occur, 
and are quite appreciable, there is abundant evidence to prove, 
and in the following table we have endeavoured to collect it :— 
