AGRICULTURAL CHEMISTRY. 137 



atmosphere is concerned, almost entirely in the form of ammonia. 

 This substance, familiar under the common name of hartshorn or spirits 

 of hartshorn, is a compound of nitrogen and hydrogen, and is charac- 

 terized by its alkaline or basic properties, having a caustic burning- 

 taste and uniting with avidity to acids, forming a large class of salts. 



In the atmosphere, in presence of an excess of carbonic acid, it 

 cannot occur in the free state, but always exists as bicarbonate of 

 ammonia, the same form in which it usually constitutes ''salt of harts- 

 horn" or "smelling salts." 



Bicarbonate of ammonia may not only occur in the solid state as a 

 white powder, but also readily assumes the condition of a gas, as is 

 evident from the volatile pungency of smelling salts. It is readily 

 dissolved to a very great extent by water ; but as readily evaporates 

 from solution again, leaving the water almost entirely free from it. 

 For this reason its amount in the atmosphere is so variable and so 

 small, it being removed by every shower of rain or deposition of dew 

 and again restored by warmth and wind, or such causes as favor 

 vaporization. 



In fact it is not by examining the air itself that we gain any ade- 

 quate idea of the amount of ammonia it may furnish to vegetation. 

 "We must rather look to the atmospheric waters, to dews, rains, and 

 fogs, in order to estimate this matter rightly. In rain water (the entire 

 fall) the quantity of ammonia is also quite variable, ranging in the 

 country from 4 to 19 parts in ten millions: while in the rain falling in 

 cities a 10 times larger amount has been observed. — (Boussingault, 

 Bineau, and Way.) 



In the first portions of rain or in slight showers, as Avell as in fog 

 and dew, the proportion of ammonia is considerably larger. Thus, in 

 the first 10th of a slow falling rain, Boussingault found 6G parts in 

 10 million of water; in dew, he found 62, and in fog 72, and in one 

 extraordinary instance 497 parts of ammonia in 10 million of water. 



Way has determined the entire amount of ammonia contained in 

 the rain water that fell during the years 1855 and 1856 at Rotham- 

 stead, 20 miles from Linden. He found that the water which fell on 

 an acre of surface contained in 1855, 7.11 pounds, and in 1856, 9.53 

 pounds of ammonia. 



The evidence that ammonia is capable of absorption and assimila- 

 tion by the plant is as various as it is conclusive. Numerous field ex- 

 periments made with artificial ammonia-compounds, as well as the 

 fact that all animal manures in the very process of decay, whereby 

 they appear first to acquire their full activity, yield this body in 

 abundance — practically establish the point; nor are there wanting 

 more precise investigations. 



Ville especially, also Chlebodarow, have shown that the addition 

 of ammonia to the ordinary atmosphere, as well as watering with its 

 dilute solution greatly increases the mass of vegetation produced, 

 and makes the same much richer in albuminoids. Ville has intro- 

 duced the use of ammonia into conservatories with quite striking 

 effect, diffusing into the air of the green-house from two to four 10- 

 thousandths of its weight of carbonate of ammonia by placing a lump 

 of this salt upon the steam pipes that supply the space with heat. 



