air,
bristles, &c., although rich in nitrogen, possess a comparatively low
manurial value. The home production of these articles may be estimated
at 6000 to 7000 tons.

_Scutch._

Scutch is the name given to a manure made from the waste products
incidental to the manufacture of glue and the dressing of skins. It
contains about 7 per cent of nitrogen, and is manufactured in London to
the extent of several thousand tons annually.

_Shoddy and Wool-waste._

Shoddy, which is a manure made from waste-wool products, is a material
largely manufactured in this country, and which was formerly (it is now
used to a considerably less extent) used to a large extent as a manure.
Its annual production amounts to about 12,000 tons. There are three
qualities,--the first containing 8 to 12 per cent of nitrogen; the
second, 6 to 8 per cent; and the third, 5 to 8 per cent. Shoddy is by no
means a very valuable manure. Woollen-waste products were formerly much
richer in nitrogen than is now the case. This is due to the fact of the
adulteration with cotton, now so prevalent in the manufacture of woollen
goods. Pure woollen rags should contain 17 to 18 per cent of nitrogen.
It has been strongly recommended to treat woollen waste with caustic
alkali before being used as a manure, in order to render their nitrogen
more quickly available; and there is a good deal to recommend this
treatment. When wool-waste is applied as a manure, it should in every
case be in autumn, so as to allow as long a period as possible to elapse
before it is required for the plant's growth.

Leather has also been used as a manure. Its nitrogen may be stated at
from 4 to 6 per cent; and it may safely be described as of all materials
used as nitrogenous manures the least valuable. Leather is, from its
very nature, admirably adapted to resist decomposition when applied to
the soil, and unless it is reduced to a very fine condition, might be
trusted to remain undecomposed for a long period. Torrefied leather,
however, is probably of greater value. It is obtained in the same way as
torrefied horn, already referred to--namely, by treatment with steam.
The grease and fatty matters which so largely aid it in resisting
decomposition being extracted, it is much better suited for manurial
purposes than ordinary leather. Torrefied leather contains from 5 to 8
per cent of nitrogen.

_Soot._

A manure which has long been used and highly esteemed is soot. Obtained
in t