162 On the Composition of Waters of Land-Drainage. 



5. In accordance with previous experience, more nitric acid 

 was found in the drainage-water from the plots to which the 

 larger quantities of ammonia-salts had been applied than in that 

 from the plots on which smaller quantities had been used. 



Other particulars which will be noticed in the composition of 

 the drainage-waters of this last series fully confirm the statements 

 already made. 



The quantity of water which passes through the drains in the 

 course of the year, as may be readily conceived, varies a great 

 deal in different soils, according to the distribution of the rain 

 in the year, and the quantity which falls at one period. The 

 researches of Maurice of Geneva, Gasparin at Orange, Dalton in 

 Manchester, Dickinson in Hertfordshire, and, more recently, by 

 Mr. Risler of Geneva and by Messrs. Lawes and Gilbert, who 

 have all endeavoured to determine the relative quantity of the 

 rainfall which escapes into the air by surface-evaporation, and 

 that which passes through the land into tjie drains, do not supply 

 ■data from which an average estimate can be made. In the ab- 

 sence of satisfactory evidence, from which might be calculated the 

 probable amount of water which passed annually through the 

 drains of the different plots of the Experimental Wheat Field at 

 Rothamsted, it is impossible to determine precisely the actual loss 

 of fertilizing matter which the several plots sustained by drainage. 

 It has been shown that the amount of nitrogen which passes into 

 the drains, in the form of nitrates, is considerable when the land 

 had been manured with ammonia-salts or with nitrate of soda. 

 Messrs. Lawes and Gilbert, in a long series of experiments on 

 the continuous growth of wheat on the same land, and on barley 

 and meadow hay, have invariably experienced a great loss of 

 nitrogen, which could not be accounted for satisfactorily ; and it 

 will be necessary to weigh the actual quantities of water which 

 pass through the soil of a definite area, and to determine the 

 composition of the whole of the drainage, before it can be ascer- 

 tained how much of the nitrogen, which is not recovered in the 

 produce, nor accumulates in the soil, passes away with the 

 drainage-waters. 



In order to afford a ready comparison of the preceding nitric 

 acid determinations with others that have been obtained, or may 

 be obtained, in similar experiments, a Table (VI., pp. 160, 161,) 

 is given in which the amount of nitrogen as nitrates and 

 nitrites has been calculated for 100,000 parts of water. * 



We learn from the foregoing calculated results how serious 

 may be the loss of nitrogen by drainage when ammoniacal-salts, 

 as nitrates, are liberally applied to the land in autumn, and 

 there is much wet weather during the winter ; or even when they 

 are applied in the spring, if heavy falls of rain should set in. My 



