Composition of Waters of Land- Drainage and of Rain. 147 



one of the instances of waters collected by Mr. Paine, say, for 

 instance, the sample No. 7, which contained upwards of 11 

 grains of nitric acid in the gallon, we shall see how very short 

 the rain-fall is of accounting for this quantity. In effect, the 

 whole quantity of nitric acid falling in rain at Rothamsted last 

 December was 664 grains, which would be contained in 60 

 gallons of the drainage- water collected at the end of that month 

 at Farnham ; Avhereas nearly 20,000 gallons of water must have 

 passed through the drains of each acre of land during the two 

 days when the samples were collected, a quantity which must have 

 carried with it upwards of 200,000 grs. (30 lbs.) of nitric acid. 



One question for which these rain-waters were examined is 

 answered. Tlie nitric acid brought down by rain is totally 

 inadequate to account for that found in drainage-water. Is it 

 then formed in the soil from the nitrogen of tl;e air ? or abstracted 

 from the air by the soil ? or is it derived from manure ? 



With the two former of these questions we need hardly trouble 

 ourselves, since the third supposition is capable of an answer so 

 decidedly affirmative. 



There is no doubt that when air containing nitric acid in the 

 state, as it would be, of nitrate of ammonia, comes in contact with 

 the soil, tlie nitric acid would be retained by the soil, and thus a 

 quantity of this substance might be accounted for. 



Again, it is possible that, under the influence of the porous 

 soil and the alkalies which it contains, the niti'ogen of the air 

 may be oxidated ; and, in the absence of better reasons, we 

 might fly to either of these for an explanation of the nitric acid 

 in drain- water ; but in the instances before us the effect is too 

 plainly traceable to manure. 



It we conq)are the analysis of the samples from Mr. Paine 

 with the history of the fields, we shall find that the largest 

 quantity of nitric acid (namely, 14, 12, and 11 grains per gallon) 

 is found where the land had been heavily manured with horn- 

 shavings, rags, rabbit-sl<in waste, or some such animal sub- 

 stance. On the other hand, in two samples from Mr. A eland, 

 where no manure had been applied, we find tlie nitric acid barely 

 exceeding rj a grain in the gallon. 



Again, of four soils, in other respects alike, from which water 

 was collected by Mr. Wren Hoskyns, the two, which had received 

 guano, furnish water containing 4i grains of nitric Jicid per gal-. 

 Ion, whilst those which had not been so treated contain only 

 about 1 grain each. I fear that this evidence is too strong to 

 permit a doubt that it is the nitrogen of manure that is thus run- 

 ning in the drains.* 



* On the 12th of November, that is, six weeks before the samples of water were 

 collected, Mr. Paine sent mc several soils for exaiiiiii:itioii,iu aid of another inquiry 



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