WATER 



47 



pure oxygen, while in ordinary air the nitrogen dilutes the 

 oxygen and thus weakens its action. 



Oxidation. In the series of experiments we have just 

 performed, burning was simply a union of oxygen with the 

 substances burned, but all around us this union with other 

 substances is taking place without producing any flame. 

 You are all familiar with the fact that iron rusts. This 

 is caused by the union of iron with oxygen. 

 Such oxidation is relatively a slow oxidation. 

 A similar process of oxidation attends the 

 decay of organic matter. In the case of 

 combustion the action is much more rapid, 

 and both heat and light are given off. 



Water. Every boy and girl knows that 

 water is necessary for the life of both plants 

 and animals. This can easily be proved by 

 allowing some living plant to wilt, and then 

 adding a moderate amount of water to the 

 pot in which it grows. What causes the 

 leaves to raise themselves? We say that 

 the plant takes up water. This is true, al- 



. 1-1 Amount of water 



though we cannot at this time explain what in the human 

 happens inside of the plant. Any boy or 

 girl who has had to go without water for several hours 

 knows how necessary it is and how uncomfortable one 

 can be without it. In the World War water played 

 a striking part, especially in General Allenby's campaign 

 against the Turkish army in Palestine. The Turks had a 

 saying that " The Christians will not capture Palestine 

 until the Nile flows into the Jordan." This meant, of 

 course, that they would never capture it, because the 

 Turks believed that such a thing was impossible. But 



