al, and well made and well preserved farm-yard manure will
generally be found to differ comparatively little in value; and when
bought at the ordinary price, the purchaser, as we shall afterwards more
particularly see, is pretty sure to get full value for his money, and
the specialities of its management are of comparatively little moment to
him. But the case is very different when the person who uses the manure
has also to manufacture it. The experiments already quoted have shown
that, though the manure made in the ordinary manner may, weight for
weight, be as valuable as at first, the loss during the period of its
preservation is usually very large, and it becomes extremely important
to determine the mode in which it may be reduced to the minimum.

In the production of farm-yard manure of the highest quality, the object
to be held in view is to retain, as effectually as possible, all the
valuable constituents of the dung and urine. But in considering the
question here, it will be sufficient to refer exclusively to its
nitrogen, both because it is the most important, and also because the
circumstances which favour its preservation are most advantageous to the
other constituents. In the management of the dung-heap, there are three
things to be kept in view:--First, To obtain a manure containing the
largest possible amount of nitrogen; secondly, To convert that nitrogen
more or less completely into ammonia; and thirdly, To retain it
effectually.

As far as the first of these points is concerned, it must be obvious
that much will depend on the nature and quantity of the food with which
the animals yielding the dung are supplied, and the period of the
fattening process at which it is collected. When lean beasts are put up
to feed, they at first exhaust the food much more completely than they
do when they are nearly fattened, and the manure produced is very
inferior at first, and goes on gradually improving in quality as the
animal becomes fat.

When the food is rich in nitrogenous compounds, the value of the manure
is considerably increased. It has been ascertained, for instance, that
when oil-cake has been used, not less than seven-eighths of the valuable
matters contained in it reappear in the excrements; and as that
substance is highly nitrogenous, the dung ought, weight for weight, to
contain a larger amount of that element. That it actually does so, I
satisfied myself by experiments, made some years since, when the