OXYGEN. 147 



by the combustion of one portion of the paper, is not 

 communicated to the next, but passes off into the air. 

 But if the taper be held with the flame downward, 

 each particle in turn receives the stimulus of heat ne- 

 cessary to combination, and the whole is consumed. 



345. DECAY OF LEAVES AND WOOD. 



What causes 



the decay of The decay of leaves and wood, is a sort 

 of slow combustion, but not sufficiently 

 vigorous to produce light and heat. In this case, as in 

 the ordinary combustion of wood or coal, the particles 

 which have combined with oxygen, pass off into the 

 air, in an invisible form. 



346. BLEACHING. Bleaching may also 



How may . * 



bleaching be be regarded as a kind of slow combustion. 

 On exposing cloth to sun and air, its color- 

 ing matter is gradually burned up, by the atmospheric 

 oxygen. 



347. OXYGEN A PURVEYOR TOR PLANTS. 

 oxygen\ a ^ nas been seen that both in combustion 

 purveyor for an( j d ecaVj the oxygen of the air combines 



with the particles of leaves, and wood, and 

 coal, and passes off with them in an invisible form. It 

 flies off with them into the air, and yields them again 

 to living plants, to produce new leaves and flowers, and 

 fruits. Indeed, they are entirely dependent, for their 

 support, on what they thus obtain from the death and 

 decay of their predecessors, through the agency of this 

 ever active purveyor, the oxygen of the air. But for 

 the fact that the particles of vegetable and animal mat- 

 ter, can thus be used again and again, the supply would 



