260 PREPARATION OF MANURE. 



of regulated fermentation, must not however be estimated too hignly ; 

 when the decomposition is carefully conducted, the mass having 

 been well trodden and properly damped, the loss is really very small. 

 The gentle fermentation, secured by these means, has characters 

 which differ essentially from those that accompany the rapid putre- 

 faction which never fails to take place when matters are not well 

 managed. As an example of the rapid and injurious fermentation 

 of which I speak, I may cite that which frequently takes place in 

 piles of horse-dung : everyone must have seen such dung-hills 

 loosely thrown together, left to themselves, without any addition of 

 water, acquiring a very intense heat in the course of a few days, 

 and have even heard of their taking fire. I have seen piles of this 

 kind reduced to their merely earthy constituents! Such are never 

 the results of the moderate and gradual decomposition which farm- 

 dung ought never to exceed. ^Vhen the pit or stance is emptied, 

 in which a slow and etjual fermentaii(m has taken place, the superior 

 layer is seen to be very nearly in the same st:iie in which it was 

 when it was piled ; the layer immediately beneath this one is chang- 

 ed in a greater degree, and sometimes exhales a slight ammoniacal 

 odor. In the lower strata, the modification is yet greater in dciiree : 

 the straw has lost its consistency, it is fibrous and breaks into pieces 

 with the greatest ease ; the mass is also progressively darker in 

 color as we go deeper, and on the grt>und it is completely black : 

 the smell which this j)art of the heap exhales, is that of sulphuretted 

 hydrogen, and when it is tested, sulphate of iron is discovered ; no 

 doubt these sul[)hurous products are all the consequence of the de- 

 composition, under the influence of the organic mailer, of the sul 

 pbales which were contained in the manure. This is the sign by 

 which I know that firm-dunii is duly prepared ; the presence of 

 sulphurets and of the hydrosulphate of ammonia will have no ill 

 etfect upon vegetation ; for scarcely is the manure si»read upon the 

 ground, than these products are changed into sid[)hates, and then 

 the manure emits that musky smell which is })eculiar to it. Fur- 

 ther, there is no doubt but that the slate in which a carefully tended 

 dung-heap is found in the end, is due to the circumsiances in which 

 it has been placed and ki'pt during the whole time »)f its preparation ; 

 its constituent elements would hive jroiie through a t»»l.illy ditferenl 

 course in the progress of their moilificaiitm had ihey been left ex- 

 posed to the op<Mi air. To be satisfied of this, it is enough to re- 

 mark the powerl'ul and purely ammoniacal smell which meets us in 

 a warm stable, especially during the summer season, upon the ground 

 of which the urine of the animals it contains is left to decompose. 



From what has now been said, it will be mulerslood how deslnie- 

 tive to good manure is the custom which obtains in certain countries 

 of turning dung-heaps frequently, of airing them as it were, in order 

 to hasten «lecoiniM)sitiiMi. Treated in this way, stable litler, &.('.., 

 does in fact decompose much more rapidly ; but il does so, and i 

 own thai I do not myself clearly perceive the object proposed by it, 

 *t the ex])ense of the quality ; for it is very evident thiit the volatile 



