214 THE CHEMISTRY OF CREATION. 



ture of foreign gases in the air to both man 

 and vegetation. Possibly, had the atmosphere 

 been created for man alone, and could he have 

 existed on a different description of food to the 

 present, it might have been unnecessary to have 

 cast any other ingredients into its composition. 

 But the earth was to be adorned with plants, 

 and these were destined to supply man with a 

 pure, agreeable, and nutritious food. Vegetation 

 cannot exist in a pure atmosphere of oxygen 

 and nitrogen for any length of time, much less 

 thrive, blossom, and produce fruit. A provision, 

 therefore, was necessary for its wants. Yet 

 here another difficulty presents itself. The gas 

 which proves most nutritious to vegetation is 

 one which is deadly in its effects on the animal 

 tribes ! This gas is Carbonic Acid. The room 

 capable of containing one hundred cubic feet of 

 air, if filled by a mixture of ninety cubic feet of 

 air and only ten of this gas, would be speedily 

 fatal to any human occupant. How was this 

 difficulty to be surmounted? How was vege- 

 tation to live, and man not to die? By the 

 most beautiful adjustment this problem has 

 been solved, for it is found that a proportion of 

 carbonic acid gas, which appears disproportion- 

 ably small, and is in reality so minute as to be 

 altogether without effect upon the human con- 

 stitution, yet at the same time sufficiently great 



