THE SOIL MAKERS 9 



How the atmosphere assists. Just as soon as the first 

 rocks were exposed to the weather, remarkable changes 

 then resulted. The rocks, after long exposure, crumbled 

 somewhat ; just a few particles, a few tiny grains from 

 time to time fell apart from the whole and dropped to a 

 lower level to be carried away by water; or they were 

 picked up and carried away by the wind when it rose 

 in sufficient force to defy the mighty giants of rock forma- 

 tion. Of course the wind accomplished but little with 

 each attack. But the wind is ever young ; it never grows 

 old, and a thousand years of trial weaken it not. These 

 tiny particles the first released from rock represent the 

 beginnings in soil making. And ever since the time, 

 who shall say how long? that these first particles were 

 given to the wind, the weather has been at work making 

 soil. 



The atmosphere assists in soil making because of the 

 chemical action of the gases that compose the air and of 

 the moisture or vapor it holds. The two important gases 

 that are so powerful in making soil are oxygen and car- 

 bonic acid. They are always at work ; they have been at 

 work from the very beginning of time ; and so long as 

 life"* exists, from the tiniest plant up to the finest devel- 

 oped type of man, oxygen will be required for the work 

 of the world. 



Oxygen forms oxides by combining with nearly all 

 sorts of materials that are found in the earth. You know 

 how quickly iron rusts when exposed to the air, especially 

 if moist an oxide of iron has resulted : not that the iron 

 has been destroyed nor the oxygen of the air that com- 

 bined with it, but the two have united and formed a new 

 chemical compound, powdery in texture and now in a 

 form to be easily combined with acid so as to become 

 food which plants may use. 



