188 THE STORY-BOOK OF SCIENCE 



the sunshine and get into the rain under the clouds. " 

 "Sometimes that would be possible, but more 

 often not, because clouds can cover large areas. Be- 

 sides, they travel, they go from one country to an- 

 other, with such speed that the best horseman could 

 not follow them in their course. You have all seen 

 the shadow of the clouds run over the ground when 

 the wind blows. Hills, valleys, plains, water- 

 courses, all are crossed in less than no time. The 

 shadow of a cloud passes over you at the moment 

 you reach the top of a hill. Before you have taken 

 three steps to descend into the valley, the shadow, 

 with giant strides, is mounting the opposite slopes. 

 \Ylio could flatter himself that he could follow the 

 cloud and keep under its cover? 



"If rain sometimes falls over great stretches of 

 country, it is never general, absolutely. If it should 

 rain at one time over a whole province, what is that 

 compared with the earth? A clod compared with 

 a large field. Chased by the wind, clouds run hither 

 and thither in the vast spaces of the atmosphere. 

 They travel, and on their way throw a shadow or 

 precipitate rain. Where they pass there is rain; 

 everywhere else, no. In the same place there can 

 even be both rain and fine weather, according as one 

 is below or above the clouds. You know that on a 

 mountain-top the clouds are sometimes beneath one. 

 The plain under the clouds may receive a hard 

 shower, while on the summit the sun shines without 

 a single drop of rain." 



"All that is easily understood/' said Jules. "It 

 is my turn now, Uncle, to ask you a question. From 



