429 



П. Local and temporal variations of the atmospheric 



percentage of carbonic acid, with special reference to the 



Arctic conditions. 



It will be sufflcient for my purpose here to enumerate the 

 chief factors, which may in certain localities exercise an influence 

 upon the percentage of CO.^ in the air. The matter has been 

 fully discussed in several papers of recent date M. 



1. The organic life. Assimilation and dissimilation gene- 

 rally counterbalance each other pretty nearly. The percentage 

 of carbonic acid in the air rises slightly during the night and 

 decreases during the day, and a corresponding annual period 

 has been found by some Authors, but the variations observed 

 were very small. Amidst abundant vegetation the percentage 

 may fall below the ordinary value, and in large towns it is 

 always somewhat above it, though generally not higher than 

 0.04 to 0.05%. 



In Arctic regions both the assimilatory and the dissimilatory 

 processes only attain very small dimensions, but there can be 

 no doubt that during the long uninterrupted summer-day 

 assimilation exceeds dissimilation. The organic life cannot 

 therefore have contributed in the least to the high percentages 

 of carbonic acid observed in the Island of Disko during my 

 journey. 



2. Carbonic acid eliminated from the ground. The atmo- 

 sphere of the ground is, as a rule, very rich in carbonic acid, 

 chiefly produced by the decay of organic substances. Under 

 certain conditions — low barometric pressure — considerable 

 quantities may be given off" to the air, but in most cases the 

 gas is so rapidly removed by the wind and mixed with the 



M Palmquist, Bihang Svenska Vet. Akad. Handl. Bd. 18 Afd. И. 

 André, Öfversigt Svenska Vet. Akad. FörJumdl. 1894 p. 355. 

 S ACH SSE, Lehrbuch der Agrikultur chemie. 

 WiLi/iAMS, Ber. d. deutsch, ehem. Ges. Jahrg. 30 p. 1450. 



