135 



It is evident that there is no nppreeiahle differenee between the 

 warm and eokl seasons. A sli<>ht addition is to be made to the 

 above table, in order to inehule the quantities of nitrogen contained 

 in the water of fogs and dew. The quantities under the eohnnn 

 " Nitric acid "' inchides such nitrites as become converted into nitrates 

 in the hiboratorv analysis. The great variations in the successive 

 seasons depend ujjon the variations in rainfall (juite as nnich as upon 

 the variations in the quantity of nitrogen j^er liter, or the variations 

 in the atmospheric constituents. 



The variations in the (luantity of nitrogen brought to the soil by 

 the rainfall in ditt'erent parts of the world is shown in the following- 

 table, as quoted by Marie-Davy from the memoir of Messrs. LaAves, 

 Gilbert, and Warington, on the composition of the rainfall at T\oth- 

 amsted. This table shows that the richness of the rain in nitrogenous 

 compounds varies geographically quite as much as the quantity of 

 rain does, so that in general the ground in (iermany, Italy, and 

 France receives decidedly more nitrogen })er acre than does the 

 ground in England. A further study of the subject also shows that 

 the rain caught in cities contains vastly more nitrogen, especially 

 ammonia, than that caught in the open country. 



Quaniity of iiitrofjrii (uiminllii hroiinht to tlic xo// by rain. 



• The appreciable quantities of nitrogen shown in the above table 

 must be diminished in agricultural computations in i)roportion as 

 the rainfall carries it off into the rivers, since only that which remains 

 in the soil can be supposed to have an appreciable influence on the 

 growth of crops. 



The quantity of nitrates in rain Avater may be expected to vary 

 with the character of the climate and^may be greatest in those regions 

 where lightning is most frequent. Observations on this subject were 

 made by A. Muntz and V. Marcano (Agr. Sci., Vol. Ill, p. 2^3), who 

 showed that at Caracas, Venezuela, where thunder storms are frc- 



