74 Recent Publications on Manures. 



is, no doubt, needed as a constituent in plants, perhaps more 

 than has been yet made plain by analysis ; from its surrounding 

 the organs in the state of ammonia, in the fluids that bathe 

 them, as Liebig says, it appears also to act as a stimulant to 

 vitality, and must be a principal though not the only requisite. 



In omnivoi'ous animals, to whom a much greater proportion 

 of nitrogen is required, if confined solely or in great part to 

 animal food, it is found to produce a too excitable state of the 

 system, and not to be conducive to health. In plants, also, it has 

 been found to increase the stem and foliage, without a corre- 

 sponding increase of deposit in the roots, when light and heat 

 and the other requisites of the food are wanting. We shall see, as 

 we proceed in the essay, that carbon is derived from many 

 other substances soluble in water, in the opinion of other emi- 

 nent chemists ; and there are, besides, the salts, and other sub- 

 stances essential to plants, in manures. Nitrogen may be one of 

 the greatest sources of value in a manure, without being the only 

 source. If we confine the benefits of food to any one of its con- 

 stituents, however valuable, we shall arrive at a false conclusion; 

 as all are needed, and will have to be considered in our estimate 

 of the value of manure, as well as ammonia. 



Of the substances recommended to make a compost for pour- 

 ing the urine on, I should think peat the best, and would 

 prefer moist peat to dried peat, as being more easily decom- 

 posed. Sawdust, if of fir wood, which it generally is, contains a 

 good deal of resin, which, being an anti-putrescent substance, 

 prevents decomposition from proceeding properly : when got 

 from woods destitute of resin, I should consider it one of the 

 best, as it is then found in practice to rot easily ; that of beech 

 wood is the best of any. Tanner's bark, from its possessing 

 tannin, also resists putrefaction. It is customary for people 

 about towns, where these substances abound, to use them as 

 bedding for swine and other animals, and even to mix with the 

 manure, to increase the quantity. Any manure I have pur- 

 chased, when it happened to be mixed with these substances, I 

 have found so inferior in quality, and the sawdust and bark so 

 fresh and undecomposed after lying a long time in the dung- 

 heap, which they had deteriorated and dried by absorption, that 

 I would rather have paid the price for the diminished quantity 

 of dung by itself, and thrown those substances away. Urine, 

 however, contains more nitrogen than other manure ; and as 

 this substance is so necessary in carrying on fermentation, being 

 the basis of the fermenting principle, the sawdust and bark may 

 do better than I anticipate. I cannot speak from experience 

 as to the mixing of urine with these substances, but would 

 prefer peat, which has been found to rot so readily with hot 

 dung ; moist peat will rot more readily than dried. One of the 



