TREES OF AMERICA. 41 



and cabbages every night ; he was afraid 

 they would die, too." 



" But you do not know that it is partly 

 owing to the trees, that we get rain at all.' 1 



" To the trees, Uncle Philip ! why, how can 

 that be ? rain comes from the clouds, and not 

 from the trees." 



" Very true ; but what are the clouds ?" 



" Why, they are up over our heads, Uncle 

 Philip.' 5 



" Oh yes, I know where they are very well ; 

 but I want you to tell me what they are, if you 

 can. But I suspect that you have not learned 

 that yet." 



" No, Uncle Philip ; I believe I do not know 

 what the clouds are." 



" Well, then, I will tell you : you know that 

 water when it is heated becomes vapour ; 

 you have seen the vapour rising from the 

 spout of the tea-kettle ; now the water all over 

 the world is constantly giving off vapour just 

 as the water does in the kettle, and this 

 vapour is in fact nothing but water, made 

 very thin and light by the heat, and it always 

 becomes water again when a great deal of it 

 gets together, and there is no heat to prevent 

 it ; when a great deal of the vapour does get 



