“Air is one of the most subtle of substances; a liter of it weighs only one gram and three decigrams. That is very little: the same volume of water weighs 1000 grams; that is to say, 769 times as much. However, such is the enormous extent of the atmosphere that the weight of all the air composing it outstrips your utmost powers of imagination. If it were possible to put all the air of the atmosphere into one of the pans of an immense pair of scales, what weight do you think it would be necessary to put into the other pan to make it equal the air? Don’t be afraid of exaggerating; you can pile up thousands on thousands of kilograms; if air is very light, the aërial sea is very vast.” “Let us put on a few millions of kilograms,” suggested Claire. “That is a mere trifle,” her uncle replied. “Let us multiply it by ten, by a hundred.” “It is not enough, the pan would not be raised. But let me tell you the answer, for in this calculation numerical terms would fail you. For the great weight I am supposing, the heaviest counterweights would be insignificant. New ones must be invented. Imagine, then, a copper cube, a kilometer in each dimension; this metallic die, measuring a quarter of a league on its edge, shall be our unit of weight. It represents nine thousand millions of kilograms. Well, to balance the weight of the atmosphere, it would be necessary to put into the other pan 585,000 of these cubes!” “Is it possible!” Claire exclaimed. “I told you so! Imagination vainly seeks to picture the stupendous mass of the layer of air wound like a scarf by the Creator around the earth. Now do you know what relation it bears to the terrestrial globe—this ocean of air having a weight represented by half a million of copper cubes a quarter of a league each way? Scarcely what the imperceptible velvety down of a peach is to the peach itself. What, then, are we, materially, we poor beings of a day, who move about at the bottom of this atmospheric sea! But how great we are through thought, which makes game of weighing the atmosphere and the earth itself! In vain does the material universe overwhelm us with its immensity; the mind is superior to it, because it alone knows itself, and it alone, by a sublime privilege, has knowledge of its divine author.” ------------------------------------------------------------------------ CHAPTER LIV THE SUN EARLY in the morning Uncle Paul and his nephews climbed the neighboring hill to see the sunrise. It was still quite dark. The only persons they met in passing through the village were the milkmaid, on her way to town with her butter and milk, and the blacksmith hammering away at the red-hot iron on his anvil, while the glow from the forge illumined the darkness of the road. [Illustration: The Sun]