“I don’t grasp it any better,” said Jules.
“Nor I, it is so enormous,” assented his uncle.
“Yes, enormous, Uncle.”
“So that the mind gets lost in it,” said Claire.
“That is what I wanted to make you acknowledge,” concluded Uncle Paul.
CHAPTER LIII
THE ATMOSPHERE
“IF you pass your hand quickly before your face, you feel a breath blow on your cheeks. This breath is air. In repose it makes no impression on us; put in motion by the hand, it reveals its presence by a light shock that produces an impression of freshness. But the shock from the air is not always, like this, a simple caress. It can become very brutal. A violent wind, which sometimes uproots trees and overthrows buildings, is still air in motion, air that flows from one country to another like a stream of water. Air is invisible, because it is transparent and almost colorless. But if it forms a very thick layer through which one can look, its feeble coloring becomes perceptible. Seen in small quantities, water appears equally colorless; seen in a deep layer, as in the sea, in a lake, or in a river, it is blue or green. It is the same with air: in thin strata it seems deprived of color; in a layer several leagues in thickness, it is blue. A distant landscape appears to us bluish, because the thick bed of intervening air imparts to it its own color.
“Now air forms all around the earth an envelope fifteen leagues thick. It is the aërial sea or atmosphere, in which the clouds swim. Its soft blue tint causes the sky’s color. It is in fact the atmosphere that produces the appearance of a celestial vault.
“Do you know, my children, what is the use of this aërial sea at the bottom of which we live as fish live in water?”