oduced by the use of straw.[148] These experiments are
interesting as demonstrating the fact that in peat-moss we have a
substance which is capable of acting as an excellent substitute for the
more costly straw, and which might increasingly be used as a fodder with
great benefit to the farmer.

Another substance which has been suggested as an excellent litter is the
common _bracken-fern_. According to some analyses made by Mr John
Hughes, the bracken, especially if cut in a young state, is a substance
of considerable manurial value. When dried, it is very much richer in
nitrogen, potash, and lime than straw. Its absorbent properties,
however, are probably not so great. Where it can easily and cheaply be
had, as in many parts of Scotland and Ireland, it might well be used for
littering purposes.[149]

_Dried leaves_ have also been used as a litter. Autumn leaves, however,
contain a very small percentage of fertilising matter. This is due to
the fact that the most of their potash, phosphoric acid, and nitrogen
pass into the body of the trees at the approach of winter. According to
Professor Storer, dried leaves only contain from .1 to .5 per cent
potash,.006 to .3 per cent phosphoric acid, and about .75 per cent of
nitrogen. Leaves, however, besides being poor in manurial ingredients,
make a bad litter, as they ferment but slowly. There is in this
fermentation a large quantity of cold sour humic acid formed, which
seriously impairs the value of the manure.[150]

Having now considered the composition of the three separate ingredients
of farmyard manure--viz., the _dung_ or _solid excreta_, the _urine_,
and the _litter_--we are in a position to consider the composition of
farmyard manure. In this connection it will be well to consider
separately the manures produced by the different farm animals.

1. _Horse-manure._

The composition of horse-manure is perhaps the most uniform of all the
manures produced by the different farm animals. This is due to the fact
that the food of the horse is generally of the same kind, consisting of
oats, hay, and straw.

The total excrements voided by a horse in a day have been calculated,
according to the average of experiments by Boussingault and Hofmeister,
at 28.11 lb., of which only 6.37 lb. consisted of dry matter.[151] These
28.11 lb. contained .18 lb. of nitrogen and .92 lb. of mineral matter.
The amount of straw necessary to absorb this amount of excrement may be
stated at fro