74 



AIR 



wing top burner. At least 

 two inches of the tube should 

 be heated, and it should be 

 turned slowly so that all sides 

 may receive the same amount 

 of heat. When the glass has 

 become soft, it should be re- 

 moved from the flame and quickly bent at right angles 

 and held in this position until it has hardened. If the 

 bend is not well rounded it shows that the glass was not 

 evenly heated. The second bend is to be made in the 

 same way. 



Fill the test tube full of cold water and after properly 

 arranging the apparatus, gently heat it. The outlet tube 

 should dip into a little water. As the water is heated it 

 expands and passes over into the other test tube. Do 

 you see any air collecting in the heated tube? Where 

 does it come from? If the water is heated too much it 

 will begin to boil and may force most of itself over into 

 the other tube. It is not necessary to heat it until it 

 boils. Allow the water to cool and notice what part of 

 the tube is occupied by air. This is the air which fishes 

 use, and they could not live in water which had been 

 boiled and then cooled. 



Review Questions, 16. 



1. Which kind of soil will become the warmer in 

 the sunshine, dark colored or light colored? Which is 

 best for early planting? 



2. When is the sunshine warmer, when the sun 

 appears red or when it appears white? 



3. How many degrees away from the direction of 



