VEGETATION AND THE ATMOSPHERE 43 



and rising dough, and putrefaction, as in decaying 

 manure, produce carbonic acid gas. And it needs 

 only a light layer of manure to cause- a cultivated 

 field to give forth between one hundred and two hun- 

 dred cubic meters of carbonic acid gas per day for 

 each hectare. 



"The wood, coal, and charcoal burnt in our houses, 

 and especially the quantities consumed in the great 

 furnaces of factories — are not they also returned to 

 the atmosphere in the form of harmful gas? Just 

 think of the amount of carbonic acid gas vomited into 

 the atmosphere by a factory furnace into which coal 

 is poured by the carload! Think also- of the- vol- 

 canoes, gigantic natural chimneys which in a single 

 eruption throw up such quantities of gas that fur- 

 naces offer no comparison. It is very clear : the at- 

 mosphere is constantly receiving carbonic acid gas 

 in torrents that defy computation. And yet animal 

 life has nothing to fear for the present or for the 

 future, since the atmosphere, though continually be- 

 ing poisoned with carbonic acid gas, is at the same 

 time always being purged of it. 



"And what is the purgative agent commissioned 

 by Providence to maintain the salubrity of the at- 

 mosphere ? It is vegetation, my friends, vegetation, 

 which feeds on carbonic acid gas to prevent our per- 

 ishing and turns it into the bread of life for our sus- 

 tenance. This deadly gas, which absorbs into itself 

 all sorts of putrefaction, is the choicest of nourish- 

 ment for plant-life; and thus out of the bosom of 

 death the blade of grass builds up new life. 



