Composition of Waters of Land- Drainage and of Bain. 135 



considerable is obvious ; but it is to be mentioned that this 

 organic matter does not contain any, or at most very little, 

 nitrogen — a fact which I carefully ascertained in one or two in- 

 stances. It is, therefore, of the carbonaceous nature, that is to 

 say, resembles woody fibre and gum, or humus in a soluble con- 

 dition. And although it is pro tanto a loss to the soil, its im- 

 portance is not very great. I am inclined to think too that it 

 is in great part derived from the roots of furze, wood, or grass, 

 which must have been in the soil in large quantity when the 

 ground was first drained and broken up ; and this idea, which is 

 shared by Mr. Paine, from his knowledge of the nature of the 

 soil, is further corroborated by the fact that the largest quantity 

 (12^ grains per gallon) is found in No. 3, the history of which 

 land is tolerably evident from the name, " Furze field," which it 

 bears. 



Leaving for an instant the question of nitric acid, let us turn 

 to the third column in Table IV., which exhibits the quantity of 

 ammonia. It will be found that the largest quantity of this alkali 

 in any of these drainage- waters does not reach tIu^^'S of a grain in 

 the gallon ; that this quantity is remarkably small will be seen 

 when we reflect that a gallon contains 70,000 grains ; and conse- 

 quently the ammonia will be equal only to 1 part in 3i million 

 parts of water. This circumstance also shows how accurate and 

 careful must be an analysis which can afford any satisfactory result 

 on such a subject. The fact is, and in tliis consists the secret 

 of the similarity of the figures above, that we are not able to say 

 absolutely what quantity of ammonia is present in such cases : 

 all we can say is, that it is more than so and so and less than so 

 and so ; thus the number 0*018 in the column we know expresses 

 the maximum of ammonia in several of the samples, but it may 

 be any less number between that and 0'012, and in like manner 

 with the others. 



I cannot help feeling considerable satisfaction at a result which 

 so completely bears out my conclusions with regard to the ab- 

 sorptive powers of the soil for this alkali (ammonia) as does this 

 comparative absence of ammonia from drainage-water. That it 

 could not be entirchj absent, I have long ago explained ; but it 

 will be obvious presently, when we calculate tlie annual loss 

 occasioned h^j drainage-water, that at all events there is practi- 

 cally no loss of ammonia from this cause. 



It becomes necessary now to revert to the column 2, in which 

 the quantity of nitric acid is given ; and here — knowing that 

 nitric acid is a compound containing nitrogen, that all-imporfant 

 element of vegetation —and ( onsidering liow very great in some 

 cases, in the Table, tlie quantities of nitric aciil are — we might 

 be seriously impressed witii the significance of the latt, were it 



