I. AGRICULTURE AND RURAL ECONOMY. 375 



RELATION OF THE NITROGEN OF THE ATMOSPHERE TO 



VEGETATION. 



Deherain has been conducting certain experiments upon 

 the influence of the nitrogen of the atmosphere on vegetation, 

 and arrives at these conclusions : First, that in the course of 

 the slow combustion of organic matter, the nitrogen of the 

 atmosphere enters into combination, probably to form nitric 

 acid, which, in contact with an excess of carbonized matter, 

 is reduced, and then gives up nitrogen to the organic matter ; 

 second, that every plant which throws ofF refuse matter upon 

 the soil which sustains it furnishes the occasion of a greater 

 or less fixation of nitrogen. This reaction, continued for 

 many years, ultimately produces the accumulation, in soils 

 left to themselves, of a quantity of nitrogen sufficient to main- 

 tain a large crop of cereals; third, it is not only by the slight 

 percentage of nitrogen which it contains that dung exercises 

 an action upon vegetation, but, in addition, by the carbon 

 matter in decomposition, which constitutes its entire mass. 

 Buried under the soil, and exposed by the process of cultiva- 

 tion to the influence of the air, this organic matter becomes 

 burned, giving rise to notable quantities of carbonic acid, and 

 its combustion determines the union of elements of the air, 

 with the nitrogen of the dung, and with the nitrogen which, 

 previously floating in the atmosphere, is henceforth drawn 

 into the series of metamorphoses which lead from the soil to 

 the plant and from the plant to the animal. 3 B, December 

 21,1871,644. 



ACTION OF SOILS IN ABSORBING GASES. 



Prof. Reichardt, of Jena, has instituted a series of experi- 

 ments, with the aid of Herr Scheermesser, upon the capacity 

 of the constituents of the earth to absorb gases, and has been 

 led to the following conclusions : 1. The power of absorbing 

 carbonic acid gas exhibited by clay purified with hydrochloric 

 acid, as well as that dried at a temperature of 212 Fahren- 

 heit, or even brought to a red heat, and also that of purified 

 kaolin, is very slight, compared with that which contains hy- 

 drated oxide of iron. 2. Sand, purified with hydrochloric 

 acid, and brought to a red heat, absorbs very slowly traces 

 only of carbonic acid. 3. Mixtures of clay and sand, in a 



