248 THE STORY-BOOK OF SCIENCE 



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 aerial sea is very vast. ' ' 



"Let us put on a few millions of kilograms, " sug- 

 gested 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 calcula- 

 tion numerical terms would fail you. For the great 

 weight I am supposing, the heaviest counter-weights 

 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 pic- 

 ture 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 repre- 

 sented by half a million of copper cubes a quarter of 

 a league each way? Scarcely what the impercept- 

 ible velvety down of a peach is to the peach itself. 



