72 



AIR 



Apparatus: Two glasses or bottles, burner, stand, 

 dish for heating. 



Materials: Geranium cuttings, olive oil, cardboard. 



a. Heat the water slowly. What comes out of the 

 water long before it boils? Boil the water for two or 

 three minutes and allow it to cool. 



b. Fill one of the glasses two-thirds full of water 

 which has not been boiled, and fill the other glass two- 

 third full of the boiled water, 

 after it has become cold. Pre- 

 pare two cardboard covers, as 

 shown in the illustration, and 

 put a geranium cutting in each. 

 Pour olive oil on the surface of 

 the boiled water to a depth of a 

 quarter of an inch, being careful 



'not to get the oil upon the cut 

 end of the geranium slip. Watch the cuttings for a week 

 or ten days and note the difference between the growth 

 of roots upon the two cuttings. Do plants need air in 

 order that their roots may grow? 



28. Air in the Soil and in Water. 



If we take a handful of soil and examine it we will 

 notice that it is made up of many fine particles of irregu- 

 lar shape and size, which do not fit tightly together. Thus 

 there are left a large number of tiny holes between the 

 little particles, which all added make a large space. These 

 spaces are all filled with air. 



When the sun is shining upon the soil it becomes 

 warm and the air in it expands, and some of it comes out 

 of the soil. As the ground cools off at night, the air within 



