“Very good, Frank. You are right again. The burning of the candle has changed a certain part of the air. It has, indeed, so changed it that it can dissolve in water just as if it were sugar or salt.”
Uncle George now poured water into the outer dish until it was level with the water inside the bell-jar. Then he took out the stopper and pushed a lighted taper into the bell-jar. The taper at once went out.
Candle in Stoppered Jar—gone out.
“This shows us,” he said, “that a part of the air causes things to burn. The other part of the air does not. It puts burning things out. If we blow the fire with a bellows or fan, it burns more brightly and quickly. Why? Just because we are forcing a stream of air upon it, and a part of that stream of air is changed by the burning.”
Uncle George next put some bright iron tacks in a small dish. He poured some water out of the large dish, and placed the bell-jar in the dish. After that he added water until it was just up to his first mark on the bell-jar.
Then he floated the dish with the tacks on the water. Next he wetted the tacks with water, and then placed the bell-jar over them and put in the stopper.
“Now,” he said, “we will leave this just as it is for a few days.”
The boys watched the bell-jar every day, and this is what they saw. The water rose slowly in the bell-jar. As it rose the bright tacks turned red with rust. The water rose higher and the tacks turned redder every day.
At length it rose to Uncle George’s second mark. It rose no farther, although left for a whole week.