CIRCULATION OF MATTER. 435 



draws its supply of gaseous food from the atmosphere, 

 and through its roots, its mineral sustenance from the 

 soil. It has purified the air in the process, of gases 

 which would become noxious by accumulation, and 

 returned to it the oxygen which is the vitalizing breath 

 of the animal world. The mingled material of its 

 food, worse than worthless to animals, has, at the same 

 time, been transformed into wood and fruit, and other 

 forms of vegetable matter. 



1074. At this point, without interruption 



Explain the . 



return of mat- m the circuit, commences the return of 

 m r oshere "*' material to tne atmosphere from which it 

 was derived. Animals that feed upon the 

 fruit of the tree, already breathe much of it back 

 again to the air, while they live, and the rest is re- 

 stored by their death and subsequent decay. Leaves 

 that fall and moulder, and branches that are burned as 

 fuel, make the same return of the elements of which 

 they are composed, to the great reservoirs of the at- 

 mosphere and earth. And what happens thus to leaf 

 and fruit, happens also at last to the parent tree itself. 

 One by one its giant branches fall and moulder, and 

 melting again into the air, add to its inexhaustible 

 stores of fertility, and provide the material for a new 

 round in the grand system of circulation. 



1075. What happens beneath the single 



Illustrate the 



extent of these tree, occurs also in every flower that lifts 

 relations. ^ petals to the sun, and is a thousand 

 times repeated in every forest upon the face of the earth. 

 No limits of distance or of size, restrict the mutual rela- 

 tions and dependencies of nature. The exhaled carbon 



