3 o8 SYSTEMS OF PERMANENT AGRICULTURE 



( "Let us picture to ourselves the condition of a well-cultured farm, so large 

 as to be independent of assistance from other quarters. On this extent of land 

 there is a certain quantity of nitrogen contained both in the corn and fruit which 

 it produces, and in the mefi and animals which feed upon them, and also in their 

 excrements. We shall suppose this quantity to be known. The land is culti- 

 vated without the importation of any foreign substance containing nitrogen. 

 Now, the products of this farm must be exchanged every year for money, and 

 other necessaries of life, for bodies, therefore, which contain no nitrogen. A 

 certain proportion of nitrogen is exported with corn and cattle; and this ex- 

 portation takes place every year, without the smallest compensation ; yet after 

 a number of years, the quantity of nitrogen will be found to have increased. 

 Whence, we may ask, comes this increase of nitrogen ? The nitrogen in the ex- 

 crements cannot reproduce itself, and the earth cannot yield it. Plants, and con- 

 sequently animals, must, therefore, derive their nitrogen from the atmosphere. 



"The last products of the decay and putrefaction of animal bodies present 

 themselves in two different forms. They are in the form of a combination of 

 hydrogen and nitrogen, ammonia, in the temperate and cold climates, and 

 in that of a compound, containing oxygen, nitric acid, in the tropics and hot 

 climates. The formation of the latter is preceded by the production of the 

 first. Ammonia is the last product of the putrefaction of animal bodies; nitric 

 acid is the product of the transformation of ammonia. A generation of a 

 thousand million men is renewed every thirty years : thousands of millions of 

 animals cease to live and are reproduced 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 underground in the church- 

 yard of the Eglise des Innocens, at Paris, all the nitrogen contained in the adi- 

 pocere was in the state of ammonia. Ammonia is the simplest of all the com- 

 pounds of nitrogen ; and hydrogen is the element for which nitrogen possesses 

 the most powerful affinity.) 



"The nitrogen of putrefied 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. Ammonia in its gaseous form as well as all 

 its volatile compounds are of extreme solubility in water. Ammonia, there- 

 fore, cannot remain long in the atmosphere, as every shower of rain must con- 

 dense 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 several wet days 

 occur, the rain of the first must contain more 'of it than that of the second. 

 The rain of a thunderstorm, after a long-protracted drought, ought for this 

 reason to contain the greatest quantity, which is conveyed to the earth at one 

 time. . . ." 



"If a pound of rain water contain only one fourth of a grain of ammonia, 



