On the Composition of Waters of Latid-Drainat/c. 157 



This result is interesting' and important, for it illustrates in a 

 striking manner the beneficial effects ot farmyanl-inanure on the 

 soil in ameliorating its texture, and, generally speaking, its 

 mechanical or physical condition, in consequence of which the 

 growing crops will suffer less during seasons of drought. 

 Messrs. Lawes and Gilbert have found that the dunged soil, when 

 saturated, retained within 12 inches of the surface, an excess of 

 water which would be equivalent to about 1^ inch of rain more 

 than that held to the same depth on the unmanured and the 

 artificially manured plots in the same field, which fully explains 

 the circumstance that during the five collections of drainage- 

 waters, samples from the dunged plot could be obtained onlv on 

 two occasions. 



The thirteen samples collected by Dr. Gilbert on 29tli Decem- 

 ber were submitted to full analvses as before. No ammonia deter- 

 minations, however, were inade, as the qualitative examinations 

 showed mere traces of ammonia in all the samples, and numerous 

 determinations have been given in previous samples. The results 

 of the analyses are given in detail in Table V. (pp. 158, 159). 



1. It will be seen that the total amount of solid matter was 

 almost precisely the same in the drainage from the continuously 

 unmanured Plots 3 and 4, and from Plot IG, which was highlv 

 manured previous to 18G5, but was left unmanured in that year 

 and since. In both cases the amount of solid matter was 

 l(j grains in round numbers. In the drainage from the other 

 plots the solid matter varied with the kinds of artificial manures 

 emplojed, and ranged from 19'80 to o7"45 grains per gallon. 



2. The unmanured plots furnished drainage which contained 

 appreciable quantities of nitric acid, which, no doubt, owes its 

 origin to the decomposition and gradual oxydation of the vege- 

 table remains left on the land by the previous wheat crop. 



3. Nitrate of soda was applied as a top-dressing on Plot 9 in 

 the middle of March, and as the drainage-water from that plot 

 contained in December scarcely more nitric acid than the 

 unmanured Plots 3 and 4, it may be presumed that any excess 

 not consumed by the wheat crop was completely washed into 

 the drains by the autumn and winter rains. 



4. In the wheat experiments the ammonia-salts, on the con- 

 trary, were always sown broadcast in the autumn, and ploughed 

 or harrowed in before sowing the seed ; and it will be seen that 

 the amount of nitric acid in the drainage-water was much greater 

 on the three occasions of winter collection, soon after the am- 

 moniacal-salts were sown, and when there was no growth, than 

 on either of the two occasions of spring collection, when active 

 growth had set in and the winter rains had, no doubt, removed a 

 s:ood deal of nitric acid into the drains. 



