OF THE NITROGEN OF PLANTS. 73 



ammonia. A generation of a thousand million 

 men is renewed every thirty years : thousands of 

 millions of animals cease to live, and are repro- 

 duced, in a much shorter period. Where is the 

 nitrogen which they contained during life ? There 

 is no question which can be answered with more 

 positive certainty. All animal bodies, during their 

 decay, yield the nitrogen, which they contain, to 

 the atmosphere, in the form of ammonia. Even 

 in the bodies buried sixty feet under ground in the 

 churchyard of the Eglise des Innocens, at Paris, all 

 the nitrogen contained in the adipocire was in the 

 state of ammonia. Ammonia is the simplest of all 

 the compounds of nitrogen ; and hydrogen is the ele- 

 ment for which nitrogen possesses the most powerful 

 affinity. 



The nitrogen of putrified animals is contained in 

 the atmosphere as ammonia, in the form of a gas 

 which is capable of entering into combination with 

 carbonic acid, and of forming a volatile salt. Am- 

 monia in its gaseous form as well as all its volatile 

 compounds are of extreme solubility in water. 

 Ammonia, therefore, cannot remain long in the 

 atmosphere, as every shower of rain must condense 

 it, and convey it to the surface of the earth. 

 Hence, also, rain-water must, at all times, contain 

 ammonia, though not always in equal quantity. 

 It must be greater in summer than in spring or 

 in winter, because the intervals of time between 

 the showers are in summer greater; and when 



