"We can't," said his father, "get it all out; but we can get a part of it out by shutting the door quick. The door will carry with it a part of the air that was in the closet, and then the outside air will be spouted in, through the key-hole of the other door. Only we can't see it, as we can the water."
"No," said Rollo; "but I can put my hand there, and feel it."
"A better way," said his father, "would be to hold a lamp opposite to the key-hole, and see if it blows the flame."
Rollo tried the experiment, in the way his father had described. He went into the closet with the lamp. He held the lamp opposite to the key-hole, and pretty near to it, and then he asked Nathan to shut the other door suddenly. Nathan, who was standing all ready by the other door, which was about half open, put his two hands against it, and pushed it to, with all his strength, producing a great concussion.
"O Nathan," said his father, "you need not be quite so violent as that."
"It succeeded, father, it succeeded," said Rollo.
"I'm glad it succeeded," said his father; "but Nathan need not have shut the door with so much force."
"I wanted to drive out all the air," said Nathan.
"I'll show you how to do it," said his father.
Rollo's father accordingly arose, and came to the closet door. He opened the door wide, and then explained to the boys, that the beginning of the movement of the door, when it was wide open, did not drive out any air.