148 Agricultural Chemistry. [March, 



support of plants. As it is composed of hydrogen and nitrogen, 

 the latter enters into combination with hydrogen, oxygen and car- 

 bon, in the vegetable, to form the nitrogenous substances, as they 

 are called, of vegetables, in distinction from those which contain 

 no nitrogen, and which constitute far the greater part of vegeta- 

 bles. These nitrogenous portions, however, are of the highest 

 consequence to the animal kingdom, as, being dissolved in the 

 blood, they are used to form a large portion of the animal struc- 

 ture, as the fibrine for the muscles, the albumen for the nerves, 

 &c. The ammonia is formed tiom natural decompositions of va- 

 rious vegetable and animal matter; and being naturally in the 

 gaseous state, rises into the atmosphere, unites with the vapor and 

 carbonic acid there existing, and falls in rain and snow to the 

 earth, to be taken up by the roots of plants, or is absorbed direct- 

 ly by the foliage and stems of plants, for their aliment and nutri- 

 tion. It is for the reason just given, that the late snows of spring 

 have long been called the poor mans tnanure and blessing from 

 the skies. Thus again, the adaptation of the three natural king- 

 doms to each other, cannot fail to lead the contemplative mind 

 from this fact to the boundless wisdom which has contrived and 

 directs the whole. 



5. It is the doctrine of Liebig, that plants derive all their car- 

 bon and nitrogen from the carbonic acid and ammonia of the at- 

 mosphere. This broad assertion is denied by Johnston, in his 

 Agricultural Chemistry, and is doubted by many intelligent 

 chemists. If the doctrine is true, manures are of no importance 

 in yielding these two most important elements, carbon and nitro- 

 gen, to the vegetable kingdom, as these come from the atmosphere; 

 while water, containing oxygen and hydrogen, may be taken up 

 from the atmosphere by the leaves, or from the earth by the roots. 

 That a great portion of the water passes in the latter method into 

 plants, is obvious from well known facts. 



6. The objection toLiebig's doctrine, as rendering manures un- 

 important, is made in a note to the work of Liebig.* The reply 

 of Mr. Ruffin, there noticed, is considered wholly unsatisfactory, 

 as the note thus concludes: "Thus, though a large proportion oi 

 nutritive piinciples may be furnished by the atmosphere and wa- 

 ter, still the benefit will be limited by and in proportion to the 

 fertility of the soil; and this fertility, in force of growth, must be 

 in proportion to the additions made to the soil by man." If these 

 two elements, however, are not included in the additions made, 

 there are strong reasons for the opinion that their absence would 

 materially diminish the growth. 



• iSee Organic Chemistry, in ifg .Applications to JgriciiUure and Physiology: 

 Cambridge, 184); p. 24-5. 



