"Stop, Master Paul," said he: "we are going to exchange the globe for this cylinder, and you will see very readily that the air is heavy. Now take away the globe."
But, though Paul tried his best, he could not succeed in obeying this order. The globe remained firm in its place.
"That is still another proof of the weight of the air," said Monsieur Roger. "The globe is empty of air; and as there is no longer any pressure upon it except from outside,—the pressure of the atmosphere,—Master Paul is unable to raise it."
"He would be able to raise the glass," said Miss Miette, in a questioning tone, "but he cannot lift the air above it?"
"You are exactly right. But you are going to see an experiment which will prove it. First, however, it will be necessary to take away the globe. I am going to ask Miss Miette to turn this button, which is called the key of the air-pump."
Miette turned the key, and then they heard a whistling sound.
"It is the air which is entering the globe," said Monsieur Roger. "Now Master Paul can take the globe away."
That was true. When Paul took away the globe, Monsieur Roger put in its place the cylinder closed by the bit of bladder. Then he worked the handle of the machine again. As the air was withdrawn from the interior of the cylinder, the membrane was heard to crackle. Suddenly it burst, with a sort of explosion, to the great surprise of Miette and the amusement of everybody.
"What is the matter?" said Miette, eagerly.
"The matter is," answered Monsieur Roger, "that the exterior air weighed so heavily upon the membrane that it split it; and that is what I want to show you. The moment arrived when the pressure of the atmosphere was no longer counterbalanced by the elastic force of the air contained in the cylinder. Then that exhausted all the air, and the atmosphere came down with all its weight upon the membrane, which, after resisting for a little while, was torn."