388 THE UNIVERSE. 



startle one ; it seems as if it must bring on an entire de- 

 struction of animal life. But by the side of the disturbing 

 element Providence has placed the means of reparation ; 

 the mantle of verdure on the globe remedies all the disor- 

 ders called forth by the animal kingdom ; each plant repre- 

 sents a regular machine for purifying the air. 



Plants require a large quantity of carbon for their 

 nourishment and the formation of their solid framework. 

 For this purpose they absorb all the carbonic acid they can 

 find in the air, and then fix its carbon in their tissues by 

 exhaling the oxygen ; a twofold action, in the course of 

 which they render the air wholesome, and regenerate it by 

 restoring the vital gas which animals absorb, and removing 

 the poison which they continually diffuse. 



This harmonious contrast will strike every one, and we 

 see that it is destined to counteract the incessant changes 

 which the animal kingdom introduces into the atmosphere, 

 and to protect it from all serious perturbation. According 

 to M. Brongniart, the law of equilibrium is such at this mo- 

 ment that plants seem to pour into the atmosphere as much 

 oxygen as animals consume. 



Nothing is easier than to estimate the quantity of oxygen 

 which plants distil at every pore into the atmosphere. For 

 this it is only necessary to put one under a bell-glass filled 

 with water; as soon as it is exposed to the light, all its 

 foliage becomes covered with bubbles of gas which are dis- 

 engaged from it, and rise without ceasing to the top of the 

 vase. If we now analyze the product collected there, we 

 find, from the brilliancy it gives to bodies in a state of igni- 

 tion, that it is oxygen, and in possession of all its attributes. 



