shine] ELEMENTARY SCIENCE 275 



the volume of air. The children realized, too, that a room should 

 be well ventilated, especially if many gas jets are burning. I ex- 

 plained to the children that a bird would die of suffocation, too, 

 if given only a small volume of air. 



About a week later the children told of a poor foreign family 

 that had been wiped out because they were ignorant or forgetful 

 of this principle. The burners of the gas stove and several gas 

 heaters had been lighted, on a cool autumn evening, and the fam- 

 ily were sleeping while all the windows were closed. The time was 

 about five in the afternoon. Later, when some one called and 

 forced the door, not only the family but also the pet house dog were 

 found dead. The children unanimously agreed that an open win- 

 dow would have saved the lives of that unfortunate family. 



EXPERIMENT FOUR 



In this experiment and the two following we established the 

 principle that heat was an expansive force. We sought to prove 

 that heat would expand a liquid. A Florence flask filled with 

 water and closed with a rubber stopper was used. A glass tube 

 was thrust through the rubber stopper so as' to project about an 

 inch into the flask and extend about a foot out of it. The height 

 of the water in the tube was marked with a rubber band. Then 

 we heated the water with a Bunsen burner and we found that the 

 water rose about an inch above the rubber band. If the water is 

 allowed to cool it will drop back to its lower mark. This experi- 

 ment illustrates the principle of the hot water heating system and 

 ocean currents. 



EXPERIMENT FIVE 



We used two brass screw rings to show that heat will expand a 

 solid. Each was screwed into a wooden handle. The smaller 

 ring was of such a size that if it were one-sixteenth of an inch less 

 in diameter, it would just slip through the larger ring. As 

 it was, it failed to pass through the larger ring. However, 

 when the larger ring was heated to a red heat in the Bunsen flame, 

 it expanded just enough to allow the smaller ring to pass through. 

 Then when water was poured on the larger ring, it contracted and 

 the other ring could not pass through. Thus we proved the con- 

 verse: that cold contracts. We also spoke of the expansion of 

 rails, the Brooklyn Bridge, and even of our own bodies in summer 



