"How can we make it go to the bottom?"
No one could tell. The children looked puzzled.
"Let us see what this will do," and, taking the glass from Susie's hand, Uncle Robert turned it over the cork, pressed it down into the water as far as it would go, and held it there. Looking through the glass, they could see the cork lying on the bottom of the pan.
"Why, Uncle Robert!" exclaimed Susie, "what—how—"
"It's the glass that does it," declared Donald.
"But the glass doesn't touch the cork," objected his uncle.
"There's air in the glass," said Frank, who had been looking at it quietly as the others talked. "That is what presses it down."
"If it's air," said Donald, "why didn't it go down before the glass was put over it? There was just as much air about it then, and more, too."
"Let go of the glass, uncle," said Frank, "and see what it will do."
Uncle Robert did so, and the glass instantly turned over, while a big bubble of air escaped through the water.