"Because it needs air. Master Paul has just exhausted the air necessary to the combustion of the candle; but the wick still smokes, and we are going to see if the smoke which it produces will rise or fall."
Everybody approached the globe, full of curiosity.
"It falls," cried Miette, "the smoke falls."
And in fact, instead of rising in the globe, the smoke lowered slowly and heavily, and fell upon the glass disk of the air-pump.
"Well," said Monsieur Roger, "you see that I was right. In a vacuum smoke falls: it falls because it no longer finds itself in the midst of air which is heavier than it and forms an obstacle to its fall. In the same way the cloud in the sky above the château would fall if we could exhaust the air which is between it and us."
"I am very glad that we cannot," cried Miette.
"And why are you very glad?" asked Madame Dalize.
"Because, mamma, I don't wish any rain to fall."
"Does Miss Miette think, then," said Monsieur Roger, "that if the cloud fell rain would fall?"
"Certainly," answered Miss Miette, with a certain amount of logic. "When the clouds fall they fall in the form of rain."