14 MODERN* HIGH FARMING. 



elements to form the carbon-hydrates glucose, cellulose, dextrine 

 and starcli, or the hydro-carbons oils, fats, essences and resins. 



Carbonic acid gas exists in the atmosphere in the proportion of 

 four 10,000lhs, and is an union of carbon and oxygen formed 

 by combustion, respiration, or fermentation. All kinds of fuel con- 

 tain large proportions of carbon, which, combining with the oxygen 

 of the air in the burning process, makes its escape in the form of car- 

 bonic acid gas. 



In the course of his experiments Boussingault discovered that 

 while under the influence of light, the leaves of plants absorb and 

 decompose this gas, and that in the dark they evolve or give back a 

 certain portion of it. 



Nitrogen is very generally supposed to be assimilated either as 

 nitric acid a combination of nitrogen, hydrogen and oxygen, 

 or as ammonia a combination of nitrogen and hydrogen only. 

 But the question is a most difficult and vexed one, which has 

 created a vast amount of speculation and upon which very few of our 

 best authorities have yet been able to agree. 



A great many of our readers will have doubtless seen performed 

 in their school-days, that interesting experiment first shown by 

 Cavendish in 1786, demonstrating the formation of nitric acid from 

 the combination of the oxygen and nitrogen of the atmosphere, under 

 the influence of the electric spark. The presence of minute portions 

 of nitric acid and of nitrates in the rain water, snow, and hail, is easily 

 explained on the theory of this important discovery, and any doubts 

 which may have existed in some minds as to the reality of the 

 combination, were effectually and finally dissipated when M. Cloe"z 

 publicly performed the following experiment in the course of a lec- 

 ture delivered to the Chemical Society of Paris, in 1861. A mixture 

 of hydrogen and oxygen gases was burnt in the presence of nitrogen, 

 and about 210 grammes of water resulted from, the explosion, 

 which, upon evaporation, was found to contain 3 grammes of salt- 

 petre. 



Numberless chemists have since that time devoted their attention 

 to the problem of fixing the nitrogen of the air in some utiliza- 



