pig-manure the reader is referred to Appendix, Note V.[141]

Before passing from this part of the subject, it may be desirable to
place before our readers the composition of the dung and urine taken
together, so that we may be able to form some idea of their relative
value, weight for weight. As the nitrogen constitutes by far the most
valuable portion of the manurial ingredients, it will be sufficient if
we compare them as to their percentage of this ingredient.

Water, Nitrogen, Calculated on
per cent. per cent. dry substance, Analyses by
per cent.
Sheep 67 .91 2.7 Juergensen.
Horse 76 .65 2.7 Boussingault.
Pig 82 .61 3.4 Boussingault.
Cow 86 .36 2.6 Boussingault.

From these figures we see that, in their natural condition, the excreta
of the sheep are the most valuable; those of the horse and pig coming
next; while those of the cow are the poorest, containing one-third as
much nitrogen as those of the sheep, and one-half as much as those of
the horse and pig. This difference, however, is due almost entirely to
the different percentage of water the excreta of the various animals
contain in their natural state; for in the dry state they are seen to
contain, with the single exception of the pig, practically the same
amount.

In conclusion, then, the important points to be noticed are--

1. That in the passage of the food through the system of the common farm
animals, only a very small percentage of the fertilising substances,
nitrogen, phosphoric acid, and potash, is assimilated and retained in
the animal body; and that, therefore, theoretically at least, the
excreta should contain nearly the same amount of fertilising matter as
the food originally did.

2. That even in the case of a fattening animal, the loss of fertilising
matter sustained by the food in passing through the system is not great.

3. That with regard to the total amount of solid excreta and urine
voided, the latter contains, as a rule, more nitrogen than the former;
the nitrogen in the urine, further, being more valuable, as it is in a
soluble condition.

4. That as regards the distribution of the ash-constituents, _lime_,
_phosphoric acid_, and _magnesia_ are almost entirely found in the solid
excrements; while the urine contains nearly all the