re-mentioned effect on the bone-black,
and _fixes_ the ammonia of the guano by changing it to a sulphate. The
twenty pounds of sulphate of ammonia added increase the amount, so as to
furnish nitrogen to plants in sufficient quantities to give them energy,
and induce them to take up the super-phosphate of lime in the manure
more readily than would be done, were there not a sufficient supply of
ammonia in the soil.

The addition of the guano, which contains all of the elements of
fertility, and many of them in considerable quantities, renders the
manure of a more general character, and enables it to produce very large
crops of almost any kind, while it assists in fortifying the soil in
what is usually its weakest point--phosphoric acid.

Prof. Mapes has more recently invented a new fertilizer called
nitrogenized super-phosphate of lime, composed of the improved
super-phosphate of lime and blood, dried and ground before mixture, in
equal proportions. This manure, from its highly nitrogenous character,
theoretically surpasses all others, and probably will be found in
practice to have great value; its cost will be rather greater than
guano.

We understand its manufacture will shortly be commenced by a company now
forming for that purpose.

[What should be learned before purchasing amendments for the
soil?

What do you know of silica?]

Many farmers will find it expedient to purchase bones, or bone dust, and
manufacture their own super-phosphate of lime; others will prefer to
purchase the prepared manure. In doing so, it should be obtained of men
of known respectability, as manures are easily adulterated with
worthless matters; and, as their price is so high, that such deception
may occasion great loss.

We would not recommend the application of any artificial manure, without
first obtaining an analysis of the soil, and knowing _to a certainty_
that the manure is needed; still, when no analysis has been procured, it
may be profitable to apply such manures as most generally produce good
results--such as stable manure, night soil, the improved super-phosphate
of lime; or, if this cannot be procured, guano.

NEUTRALS.

SILICA.

_Silica_ (or sand) always exists in the soil in sufficient quantities
for the supply of food for plants; but, as has been often stated in the
preceding pages, not always in the proper condition. This subject has
been so often explained to the student of this book, that it is only
necessar