On the Composition of JVaters of Land-Drainage. 149 



Tlie question arises, whence is the nitric acid in the latter case 

 derived? The proportion of ammonia in rain-water is too small 

 to ijive much support to the theory that the nitric acid in the 

 drainage from the unmanurcd plots of the field is derived from 

 the ammonia of the rain. In contact with the soil the ammonia 

 of the rain will, no doubt, be absorbed and become oxydised 

 into nitric acid ; but probably only a fraction of the nitric acid 

 which was actually found in the drainage is due to atmospheric 

 ammonia, and much more is likely to have resulted from the 

 gradual decomposition or decay of the roots and other vegetable 

 remains left in the soil by the wheat crop. 



4. More nitric acid was found in the drainage from the plots 

 to which ammoniacal-salts were applied in large proportions 

 than in the drainage from the plots on which they were used 

 more sparingly. Thus the drainage water from Plot 6, manured 

 with 200 lbs. of salts of ammonia, contained 4*60 grains of 

 nitric acid ; that from Plot 7, manured with 400 lbs. ammonia- 

 salts, 7-59, and that from Plot 8, manured with GOO lbs. ammonia- 

 salts, 8'0(S grains of nitric acid per gallon. 



On Plot 15 the drainage contained as much as 12*55 grains of 

 niti'ic acid, showing how large a proportion of the most valuable 

 fertilizing matter may be lost by drainage. 



5. It will be seen that the drainage from Plot 9, manured in 

 the preceding spring with nitrate of soda, contained much less 

 nitric acid than that from Plot 7, upon which the same quantity 

 of nitrogen was used in the shape of ammonia-salts. In the 

 latter 7*59 grains of nitric acid per gallon were found, whilst 

 the drainage from the nitrate of soda plot contained only o"lo 

 grains. The portion of the field which in spring had been 

 manured with aminonia-salts, it thus appears, contained a larger 

 proportion of nitrates than the plot top-dressed in spring with 

 nitrate of soda, showing that the nitrogen of the manure had 

 been removed to a greater extent by the rainfall during the 

 autumn from the nitrate of soda plot than from the plot upon 

 which the same quantity of nitrogen was employed by the shape 

 of ammonia-salts. 



(>. The proportion of lime in the different samples varied 

 considerably. Whilst the drainage from the unmanurcd Plots, 

 3 and 4, contained only 7 '14 grains of lime, that from some of 

 the manured plots contained from 16 to 19 grains. With an 

 increasing proportion of nitric acid in the drainage that of 

 lime also increased, showing that nitric acid passed off as 

 nitrate of lime. 



7. More magnesia was found in the water from the plots to 

 which sulphate of magnesia had been applied than where no 

 magnesia-salts were employed as manuring agents. 



