194 THE STORY-BOOK OF SCIENCE 



rain. When Jules tires himself working the pump 

 to water the flowers, has he ever thought that the 

 water drawn from the well and spread over the 

 ground sooner or later is dissipated in the immensi- 

 ties of the air to play its modest part in the forma- 

 tion of clouds ?" 



"In watering my garden," answered Jules, "I 

 did not think I was watering the air more than any- 

 thing else. But I see now: air is the great drinker. 

 Of the contents of a watering-pot the plants take 

 perhaps a handful ; the air drinks up the rest. And 

 that is why we have to do it all over again every 

 day." 



"And if you exposed a plateful of water to the 

 sun what would finally become of it I 9 ' 



"I will answer that," Emile hastened to reply. 

 "Little by little, the water would turn into invisible 

 vapor and there would be nothing but the plate left. ' ' 



"What takes place at the expense of a plate of 

 water, and of the moisture of the soil or wet linen, 

 takes place also, on a vast scale, over the entire 

 surface of the earth. The air is in contact with 

 damp soil, with innumerable sheets of water, lakes, 

 marshes, streams, rivers, brooks, above all with the 

 sea, the immense sea, which presents thrice as much 

 surface as the dry land. The great drinker, as Jules 

 calls it, the air, must therefore drink to satiety and 

 everywhere and always contain moisture, sometimes 

 more, sometimes less, according to the heat. 



"The air that is around us now, that invisible air 

 in which the eye distinguishes nothing, nevertheless 

 contains water that can be made visible. The means 



