470 



nitrogen with hydrogen, in the pi'oportion of one volume of nitrogen 

 and three of hydrogen, produces ammonia. It is in the form of am- 

 monia, that plants receive their nitrogen. This ammonia is furnished 

 to the roots of the plants by the decomposition of animal matter in the 

 soil, and to their leaves by the effluvia arising from decayed and 

 decaying animal and vegetable substances. This decay is continually 

 going on, and, together with the excrements of animals, supplies the am- 

 monia contained in the atmosphere. There are, indeed, some natural 

 subterranean sources of ammonia, connected with volcanic action ; 

 and ammonia is found in many springs, which, Liebig supposes, derive 

 it wholly from the atmosphere. The principal part of the nitrogen, 

 which is found in plants, is, in his opinion, obtained in the form of am- 

 monia in rain water. Though it appears that it has been discovered by 

 others, that rain water contains ammonia, yet it is believed that Liebig 

 has been the first to annoimce the fact. He goes on to show, by the 

 elements made use of in a former calculation, that by means of the 

 rain falling annually upon 40,000 square feet of soil, the field must 

 receive 80 lbs. of ammonia, or 65 lbs. of nitrogen, which is more ni- 

 trogen than is contained in the amount of crops usually produced upon 

 such a surface. The experiments made to ascertain the presence of 

 ammonia in rain water, are decisive, and this interesting fact may be 

 considered as now established. He likewise detected ammonia in the 

 juices of the maple and the birch tree ; this, being obtained remote from 

 any house, was evidently derived from the atmosphere. 



There are facts here connected with cultivation, and showing the 

 effect of different manures upon the quality of the products, which are 

 extremely curious. Different wheats are found to contain very differ- 

 ent proportions of gluten, of which nitrogen forms an important con- 

 stituent. Some French wheat was found to contain 12.5 per cent, 

 of gluten, while Bavarian contained 24 per cent. Davy obtained 19 

 per cent, from winter, and 24 from summer, wheat. Sicilian wheat 

 afforded 21 percent. ; Barbary wheat, 29 ; Alsace, 17.3 ; wheat grown 

 in the Jardin des Plant.es 26.7, and winter wheat 3.33 per cent. In 

 regard to these differences, Liebig remarks : 



" An increase of animal manure gives rise not only to an increase 

 in the number of seeds, but also to a most remarkable difference in the 

 proportion of gluten which they contain. Animal manure acts only 

 by tlic formation of ammon'a. One hundred parts of wheat, grown on 

 a soil manured with cow-dung (a manure containing the smallest quan- 



