324 Agricultural and Horticultural Chemistry. 



they were not aware that the absorption of nitrogen, by 

 plants, was essential to the formation of those compounds 

 on the presence of which, the value of nearly all vegetables 

 and plants, as articles of food, mainly depends. Chemical 

 enquiries into the compounds of nitrogen have shown, that 

 this singular element has, as it were, a reluctance to enter 

 mto combination with other substances, not uniting with 

 them under ordinary circumstances when in the free state, 

 but combining with them for the most part easily when in 

 the nascent state, or at the moment of being evolved from 

 one of its compounds in a state of decomposition. It is 

 known, for example, that the nitrogen of the air is unable, 

 under all ordinary circumstances, to unite with oxygen, 

 carbon, and similar simple substances, and from a knowl- 

 edge of this, we are led to conclude, that plants cannot 

 derive their nitrogen from that great reservoir of free nitro- 

 gen, — the atmosphere. 



"Liebig, who was the first to point out the vast impor- 

 tance of this element in the processes of vegetation, has 

 also investigated the source whence it is derived. He has 

 shown, that the nitrogen of the air cannot be assimilated, 

 but that the air always contains a minute trace of ammo- 

 nia, — a compound of nitrogen, and therefore a snbstancein 

 which it exists in a form capable of being assimilated by 

 plants. By a most ingenious series of experiments and 

 deductions, he has established the theory, that plants derive 

 the nitrogen which is necessary to their growth by decom- 

 posing ammonia and assimilating the nitrogen it contains; 

 and that the ammonia which thus supplies them with nitro- 

 gen is constantly being formed by the decay of animal and 

 vegetable substances and similar organic matters." 



Nitrogen, then, being of such vast importance in the 

 formation of all vegetable substances, and ammonia being 

 the compound which supplies this element, consequently 

 rendering it a substance of the greatest interest in vegeta- 

 ble chemistry, the necessity must appear evident to every 

 one, of preserving this gas, which is continually being 

 evolved from all animal and vegetable substances, whilst 

 undergoing decay. Owing to the very volatile nature of 

 this gas, the greater part will be dissipated and lost in the 

 surrounding atmosphere, unless it is fixed by strewing 

 gypsum or some other substance which combines with it, 

 on those materials from which the gas is escaping. The 



