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.

"There," said Frank, smiling, "I told you so!"

"Then air only presses on things when there is something like the glass
to hold it down. Is that so, uncle?" asked Donald.

"Let us see," was the reply.

[Illustration: Air Pressure. Experiment No. 2.]

Filling the glass with water, he placed a piece of paper over it, and
quickly turned it upside down. Not a drop of water fell from the glass.
The paper, now beneath the water, stayed there as though glued.

"Uncle," said Frank, "is it truly the air that holds the paper on and
keeps the water in the glass? If it presses that way everywhere, why
don't we feel it?"

"It is because it presses equally in every direction," replied Uncle
Robert. "Put your hand in this pail of water. Do you feel it pressing on
your hand?"

"No," said Frank.