"It might be," answered Donald, "but I don't see how."

Uncle Robert told Susie to put the glass in the water so that it would
all be below the surface, and, without taking it from the water, to turn
it upside down. She did so, and then began to lift it slowly out of the
water.

"See," cried Susie, "the water comes with it. The glass is full. Could I
lift it clear out that way?"

"Try it," said Uncle Robert, smiling.

But no; when the edge of the glass came out of the water in the pail,
down went the water with a splash.

"I see how it is," said Frank, who had watched it closely. "There wasn't
any air in the glass to keep the water out, as there was when we turned
it over the cork, so the water stayed in it."

"But what made it come up out of the pail?" asked Donald. "There wasn't
any air under it to press it up."

"Would the air pressing on the water around the glass make it do so,
uncle?" asked Frank, placing the glass in the water and raising it as
Susie had done. "It seems as if it might be that."

"That is what it is," replied his uncle. "The air pressing on the water
in the pail forces it into the glass, where there is nothing to keep it
from rising."