ON MANURES. 195 



plants suffer from the contact of fermenting dung; and it is 

 this well-known fact, more than from any other circumstance, 

 which deters farmers from applying dung in an unprepared 

 state. It is sometimes applied to the soil, it is true, in an un- 

 prepared state, but long betbre the crop is brought into contact 

 with it, and after it has undergone fermentation in tlie soil. 

 Though this application of dung is recommended by men of 

 science, it is performed from the very opposite principle which 

 they recommend. They recommend it because the gases 

 arising while the dung is fermenting are absorbed by the soil, 

 and are thence given out for the use of plants; on the other 

 hand, farmers perform it, because the fermentation will have 

 ceased before the crop is inserted into the ground. Which of 

 these is the more rational reason] The practical one, un- 

 doubtedly; for it is surely impossible that the slight covering 

 of earth upon the dung can prevent the escape of the elastic 

 gases, however it may retard fermentation. 



' Moreover, practice finds that fresh dung is injurious to 

 vegetation, and recent discoveries now inform us that this 

 arises from the acridity of the ammonia, which is always 

 present in unfermented dung. Fermentation drives off the 

 acrid ammonia. Fresh dung is found to injure plants by 

 burning them, which is a very appropriate term to describe 

 the action of ammonia. In like manner, stale liquid manure 

 is not so good a top-dressing to grass as fresh, or when it is 

 largely mixed with water; because science now informs us, 

 that ammonia becomes concentrated in stale liquid manure, 

 and is therefore in an injurious state for plants; and that it is 

 necessary, to mix liquid manures largely with water, in order 

 to dilute the ammonia, and allow the proper action of the 

 humic acid, which exists in large quantity in them. Again, 

 it is not an uncommon practice to cover a dunghill with earth 

 in hot weather; and this is now explained, not as it hitherto 

 has been — " that the earth absorbs and prevents the escape of 

 the carbonic acid gas" — but that a violent fermentation in the 

 dung is checked by the earth, partly excluding the atmospheric 

 air and rain water, the oxygen in either of which is indispen- 

 sable to continue the process, it being this oxygen which forms 

 the carbonic acid gas by uniting with the carbon of the dung. 

 The necessity of checking a violent fermentation in a dunghill 

 which contains a large portion of horse-dung, is to prevent it 

 being what is technically called ''fyrefangit,'" — a state in 

 which dung is nearly useless. 



