28 THE ATMOSPHERE. II. 



for the day and "0330% for the night, and similar results have 

 been obtained by other observers. Miintz and Aubin give 

 0278% as the universal average; they noticed -0273 as the 

 mean in the day and -0288 in the night." H. T. Brown gives 

 as a result of many determinations made in 1898-99, '0285 as 

 the mean and -027 and -030 as the usual limits of variation 

 in summer. ! Over the sea or in places far from vegetation no 

 such difference can be detected, and the average amount 

 (030%) is lower. Schulze, as a mean of nearly three years' 

 daily determinations of carbon dioxide in the air at Rostock, 

 found -0292%, the maximum being -0344% and the minimum 

 0225%. I 



Theoretically, assuming that the composition of the atmo- 

 sphere is not modified by any disturbing influences, the 

 amount of carbon dioxide should diminish with the height 

 above the sea-level. Experimental evidence on this point is 

 conflicting. Truchot found distinctly less at heights of 1440 

 (020%) and 1880 metres (-0172%) than nearer the sea-level 

 (0313), while recently (1899) Thierry $ found on Mont Blanc 

 0262% at 1080 metres and -0269% at 3050 metres. Miintz 

 and Aubin jj found in 1882, as a mean of many analyses, '0286 

 volumes on the Pic du Midi (2877 metres), practically the same 

 as in the plains. The earlier observers, too, found more on the 

 tops of mountains than at sea-level. It is obvious that vege- 

 tation must have a great local influence on the amount of 

 carbon dioxide and may, in some cases, cause misleading 

 indications. 



Among the many causes tending to increase the amount of 

 carbon dioxide in the air, the following are the most impor- 

 tant : 



1. Emission from volcanoes, deep springs, and other subter- 



ranean sources ; immense quantities are thus sent into 

 the atmosphere. 



2. Oxidation of carbonaceous matter; this occurs in the 



processes, of respiration of animals and plants, the 

 decay and fermentation of animal and vegetable pro- 

 ducts, and the combustion of most fuels. 



* Bieder. Central. 1883, 469. 



t Brit. Assn. Report, 1899, Presidential address, section B. 

 J Versueh. Stat. 14, 366. Compt. Rend. 129, 315. || Compt. Rend. 93, 797. 



