138 Composition of Waters of Land- Drainage and of Rain, 



It is pretty plain which were the samples from manured land.* 



We have now before us the determinations of ammonia in 

 some 12 or 14 samples of drainage water, and that of nitric acid 

 in a considerably large number, and we may fairly come to some 

 conclusion on the subject. With regard to the former there can 

 be no manner of doubt — from soils rich or poor, manured or not 

 manured, it is all the same, the quantity of ammonia in no case 

 exceeds -rf ^ths of a grain in the gallon. I regard this as conclu- 

 sive, and believe that unless in very exceptional cases, and where 

 the manure visibly runs into the drains — probably through cracks 

 in the soil — we shall not find ammonia in quantity in the waters 

 of drains. 



With nitric acid the case is different. In the instances before 

 us we have it in all sorts of quantities — from 14f grains in Mr. 

 Paine's sample No. 2 to Vo'tiths of a grain in Mr. Acland's 

 sample 2 B. The presence of nitric acid in some proportion in 

 drainage water would seem to be universal, for of nearly 20 

 samples examined not one is free from it. But we may well ask 

 at what point are we to fix the natural or ordinary quantity of 

 this substance carried off in drainage water. To that question I 

 am as yet not prepared to offer an answer, I have said before 

 that this must be considered in the light of a preliminary inquiry 

 — settling some matters and leaving others open for further inves- 

 tigation. Amongst these latter the principal are the variations 

 from time to time throughout the year and the manures which 

 more or less give rise to nitric acid. 



Attention was called just now to the variation in the quantity 

 of soda and magnesia in Mr. Paine's samples, and it was suggested 

 that they would be found in all probability to be connected with 

 the proportion of nitric acid. In effect if we examine the Tables 

 we shall find that such is the case — wherever the proportion of 

 nitric acid is large, there also the proportion of soda and mag- 

 nesia is large — the converse being also observed. The remark 

 applies perhaps more truly to magnesia than to soda, which 

 latter alkali is dependent to a great extent on the quantity of 

 chlorine present, in combination with which it occurs as common 

 salt. 



The connection of nitric acid with alkalies or earths in drain- 

 age water is simple enough — if a substance containing nitrogen 

 undergoes oxidation in the soil with the production of nitric acid, 

 this latter cannot be supposed to pass through the soil to the 

 drains without neutralization — it therefore unites with lime, mag- 



* As the "wheat crop of last year had probably taken up the guano dressing in 

 No. 3, and the field was not manured before the autumn ploughing, I have little 

 doubt that the order in which I have numbered the fields corresponds with that 

 in which Professor Way has given the figures stating the results. — C. W. H. 



