208 Progress of Agrlciiltnral Knoicledge 



be done without loss. This principle of rapid fcedinpf which 

 Mr. Childers has brous^ht forward seems well deservinir inquiry ; 

 since if it be practicable it must g:reatly increase our manure, 

 and consequently our crops, according to the bountiful provision 

 of nature, that the more meat we raise on our land, the more corn 

 we are enabled to grow ; and that thus, again, having obtained 

 more corn, the more stock in return we are able to feed. 



This brings me to the most difficult subject in agriculture, 

 which I have therefore reserved for the last. I mean manure, on 

 which it may be said that we have learnt a great deal in the last 

 four years, but know nothing ; for we have learnt many of the 

 chemical principles on which manures act, but we do not yet 

 know how to apply those principles to the daily work of the farm. 

 It is now established that the most important ingredient of 

 iarmyard dung is ammonia — the same substance as common 

 smelling-salts — known to escape very readily in the air ; and there 

 is a growing opinion that a great deal of it does so escape from 

 our farmyards, which is doubtless the case ; though I am not sure 

 whether the alarm on the subject be not somewhat exaggerated. 

 For ammonia arises chiefly from the urine of the cattle, but it 

 does not form itself until after some days; and by that time in a 

 well-littered yard it has sunk from the surface, and has been tram- 

 pled down fast, so that it can less easily evaporate. Whilst it is 

 forming itself, too, the straw begins to decay ; and it is the opinion 

 of Sprengel that an acid called the humic acid, formed from the 

 decaying litter, has the property of combining with the ammonia, 

 and removing its volatile property.* This inust be doubtful, of 

 course, and various means of fixing the ammonia have been pro- 

 posed. Sulphuric acid is one, either in the shape of gypsum, 

 which has been found not to answer, or in that of green vitriol, or 

 as a pure acid ; but these are at present only suggestions. We 

 have been also strongly urged to imitate a foreign practice of 

 using liquid manure, spread from a water-cart ; but this I be- 

 lieve to be a very doubtful innovation. For if the urine be 

 collected separately, it is the opinion of Sprengel f that a still 



'■' Where peat can be obtained, it ass;ists in fixing the ammonia when 

 mixed with the dung, according to Lord Meadowbank's process. — See 

 Journal, i., p. 147. — Mr. Dixon on Compost Heaps. 



•f- Dr. Sprengel, after describing the various methods of employing liquid 

 manure, uses these strong words: — "Whoever is obliged for want of straw 

 to collect the urine separately — whoever, if he be compelled to do this, mixes 

 no water with it, or who fails also to employ some neutralising substance to 

 combine with the ammonia which is produced in so great a degree during 

 the summer — suffers a loss of manure which exceeds all belief. It is indeed 

 only a gaseous substance, and not a solid material visible to the eye, which 

 thus escapes and is lost; but for all that it is of greater importance to the 

 plants than any other portion of the droppings." 



