CARBONIC ACID I3ST AIR. 



215 



to meet and satisfy all the requirements of the 

 most profuse vegetation, has been widely mixed 

 with the other gaseous constituents of the atmo- 

 sphere. The quantity of carbonic acid present 

 in the atmosphere is variable. Represented by 

 figures, it may be thus stated: 



In 10,000 volumes of air : 

 The maximum of carbonic acid is 6 volumes. 

 The minimum a little more than 3 volumes. 



Other observers place it a little higher, and con- 

 sider it present in the proportion of one to one 

 thousand volumes, or about one-tenth per cent. 



Carbonic acid, however, is a remarkably 

 heavy gas : so heavy, that it may actually be 

 poured like water 

 out of one vessel 

 into another, as 

 may easily be prov- 

 ed by filling a jar 

 with this gas, pro- 

 cured by action on 

 a little chalk with 

 hydrochloric acid 

 and water, and 

 holding it in the 

 position represented 

 over the mouth of another jar containing a 

 lighted taper, which will be immediately extin- 

 guished. If at the temperature of 60, and 



