that which is derived from horse-shoe nails,
and similarly worn fragments. The nails are
in the first instance made of good sound iron,
and the violent concussions which they receive,
when a horse is working over a stony
road, give a peculiar annealing and toughening
to the metal, highly beneficial to its
subsequent use for gun-barrels.

An advertisement in the Times notifies,
that "The Committee for managing the
affairs of the Bristol Gas Light Company
are ready to enter into a contract for a
term, from twenty-first December next, for
the sale of from sixteen thousand to twenty
thousand gallons of ammoniacal liquor, produced
per month at the works of the Company."
What is this ammoniacal liquor? It is a
most unloveable compound, which the gas-
makers must get rid of, whether it has
commercial value or not. After coal has been
converted into coke in the retorts of a gas-
house, the vapours which escape are
extraordinarily complex in their character; they
comprise, not only the gas which is intended
for illumination, but acids, and alkalies, and
gases of many other kinds—all of which must
be removed before the street-gas arrives at
its proper degree of purity.  By washing in
clean water, and washing in lime water, and
other processes, this purification is gradually
brought about.  But then the water, which
has become impregnated with ammonia, and
the lime, which has become impregnated with
sulphuretted hydrogen and other gases, are
dolefully fœtid and repulsive; and in the early
history of gas-lighting these refuse products
embarrassed the gas-makers exceedingly.  But
now the chemists make all sorts of good things
from them. The lady's smelling-bottle contains
volatile salts made from this refuse ammonia,
and sulphate of ammonia is another product
from the same source; the tar, which is
another of the ungracious consequences of
gas-making, is now made to yield benzole—a
remarkable volatile liquid—which
manufacturers employ in making varnish, and
perfumers employ in making that which is
honoured by the name of oil of bitter almonds,
and housewives employ in removing grease
spots, and economical ladies employ in cleaning
white kid gloves ; the naphthaline, which
annoys the gas-maker by choking up his
pipes, is made to render an account of itself
in the form of a beautiful red colouring
matter, useful in dyeing—in short, our gas
works are a sort of magical Savings' Bank, in
which commercial nothings are put in, and
valuable somethings taken out.*

* See also an article headed Gas Perfumery, in Volume
III. page 334 of this Miscellany.

Mr. Brockeden has taught us how to make
pencils out of dust. Our black lead pencils,
as is pretty generally known, are made chiefly
from Borrowdale plumbago, brought from a
mine in Cumberland. This mine is becoming
exhausted ; and a question has arisen how
the supply shall be kept up. Various
compounds have been suggested in different
quarters, but Mr. Brockeden has happily hit
upon an expedient which promises wonders.
Although pieces of plumbago are scarce,
plumbago dust is tolerably plentiful, and Mr.
Brockeden operates upon this dust.  He
presses a mass of the powder together, then
draws out the air from beneath the particles
by means of an air pump, and then presses
again with such enormous force as to convert
the mass into a solid block, which can be cut
into the oblong prisms suitable for pencils.

If a ton of lead contains three ounces of
silver—one ounce in twelve thousand ounces
—will it pay to dig out this silver,
mechanically or chemically? Will it save a penny?
Mr. Pattinson, a manufacturing chemist at
Newcastle, says, and shows that it will;
although, before his improvements were introduced,
the attempt was a losing one, unless
the lead contained at least twenty ounces of
silver to the ton.  Nearly all lead ore contains
a trace of silver, which becomes melted and
combined in the ingot or pig of lead.  Vast
are the arrangements which the manufacturers
are willing to make to extricate this morsel
of silver from the mass in which it is buried;
huge furnaces, and melting-vessels, and
crystallising vessels are provided, and elaborate
processes are carefully conducted.  The lead,
itself, is all the better for losing its silvery
companion; while the silver makes its appearance
afterwards in the form of dazzling tea-
services, and such like.

The mention of Newcastle calls to mind our
opening paragraph, relating to a certain table-
land of refuse.  The history of this useless
product carries with it the history of many
other remarkable products—once useless, but
now of great value. Thus it is. Sulphur is
thrown into a "burning fiery furnace;" it
burns away, and is converted into a gas
called sulphurous acid; this, being combined
with steam and water, becomes liquid
sulphuric acid.  So far good: there is no
refuse.  But let us go on.  Common salt, or
rather rock salt from Cheshire, is heated with
this sulphuric acid in a furnace. A peculiar
penetrating gas rises, which is muriatic acid;
the soda-makers (of whom more presently)
did not want this troublesome gas, and they
therefore sent it up aloft through the chimneys.
But the gardeners and farmers all around
complained that the muriatic acid vapours
poisoned their trees and plants, and then the
manufacturers were driven to construct
chimneys so lofty as to overtop our loftiest
steeples, in order to carry away the enemy as
far above the region of vegetation as possible.
But good luck or good sense came to their aid;
they devised a mode of combining the gas with
water, and thus was produced muriatic acid
or spirits of salt: and then this muriatic acid
was made to yield chlorine, and the chlorine
was made to form an ingredient in bleaching
powder; so that, by little and little, the once
dreaded muriatic acid gas has become a most