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4B ELEMENTS OP 



universal cultivation they receive from the industry and 

 skill of man, more especially upon the large proportion 

 of nitrogen they contain. The amount of this laiter 

 material affords the readiest test by which their agricul 

 tural value, compared with other matters and with that 

 of each other, can be tolerably well esiimalcd. 



Ordinary farm-yard manure, in its recent state, con- 

 tains a given proportion of nitrogen ; but fifteen pounds 

 of blood would yield as much nitrogen as one hundred 

 pounds of farm-yard compost. If dried blood were ta- 

 ken, four pounds would he sufficient; three pounds of 

 feathers, three of liorn shavings, five of pigeons' dung, or 

 even two and a half of woollen rags, would counterpoise 

 one hundred cf the frst-named material. Sixteen would 

 be the equivalent number for the urine of the horse, 

 ninety-one that of the cow% seventy-three for horse-dimg, 

 one hundred and twenty-five for cow-dung; while the 

 mixed excrements of either animal would correspond 

 with the fact, that the discharges of the cow offer no 

 resemblance to those of the horse, 



Besides their general relative value, namely, as to the 

 proportions of nitrogen they contain, the above matters 

 have a further special value, dependent upon the diver- 

 sity of saline and other organic matters which they sever- 

 ally contain. Thus, three of dried flesh are equal to 

 five of pigeons' dung, as far as nitrogen is concerned ; 

 but* then pigeons' dung contains a quantity of bone, 

 earth, and saline matter, scarcely present in the former. 

 Hence, the dung of fowls will benefit vegetation in some 

 instances where even horse-flesh— ordinarily regarded 

 as a strong manure — would fail. And why ? Evidently 

 because, if saline matters are deficient in the soil, an 

 excessive supply of nitrogen will not serve as their sub- 

 stitute. So the licjuid excretions contain nuich impor- 

 tant saline matter not present in solid dung, nor in such 

 substances as horn, hair, or wool ; and therefore each 

 must be capable of exercising its own peculiar influence, 

 and be comparatively useless, if deficient of those mat- 

 ters which are also found wanting — deficient, yet neces- 

 sary in the soil. This afl^ords the reason why no o?ie 



