the one got by expression from the seeds of the
Ricius officinalis, or Palma Christ!, the other
by expression and distillation by alcohol, from
the seeds of the croton Tiglii. And what the
first is our nursery knows too well in the hours
spanning Christmas-day and Twelfth Night
together in one arch of feasting, pleasure, morning
tempers, rhubarb and magnesia, and the doctor
with still nastier punishments. These are the
principal vegetable oils, of the fixed or fatty kind.

The only animal oils, properly so called, are
lard oil, tallow oil, and neat's-foot oil: and these
are obtained from the fats of the various beasts
indicated—from hog's lard, from sheep's tallow,
and from cow-heel: but the fats, or stearine, or
adipose tissue, or by what name soever it is
considered well to call them, come quite under
another heading, and do not rightfully run into
our oil-flasks. Lard oil is used for greasing wool;
tallow oil makes the best kinds of soap; and neat's-
foot oil oils church clocks admirably, because it
does not solidify at even a comparatively low
temperature, and does not soon turn rancid.

The animal oils are few, and the fish oils are
not many; but of enormous value, first, there is
train oil, which comes from the whale, the porpoise,
the pilchard, the seal, and others; an oil of
a brownish colour, disagreeable to the smell,
used for lighting, for making soft soaps, and in
the preparation of leather; also, says historical
ill nature, much valued as a winter dram by Russian
sailors, to whom a pound of tallow-candles
is as welcome as a box of bonbons to a Spanish
belle. The peculiar, and most peculiarly
disagreeable odour of train oil, is due to the
decomposition, during the homeward passage, of
the animal matter attached to the blubber, by
which is developed a certain fat composed of
glycerine and phocenic acid. Porpoise oil is
very like whale oil. Cod-liver oil is got from the
livers of the common cod, the dorse, the
coalfish, the burbot, the ling, and the torsk. In
Australia, the liver of the dugong is used instead
of the cod: but no dugong liver oil has found
its way over here. Fish oil of various kinds is
largely used for soap-making; and the famous
Naples soap is made from fish oil and potash,
giving a marvellous lather for strong beards; but
before any soap can be made, the glycerine of
the oil must first be got rid of, when the fatty
acid is mixed with alkali, and soap is formed.
In the case of glycerine soap, the glycerine is
put back again, when it combines in a different
manner. Diachylon plaster, an insoluble soap, is
only lead and oil: and ammonia and oil is a "volatile
liniment, forming a milky emulsion, and used
as a rubefacient in medicine." Are there many
who recognise in these majestic words our old
greasy friend, the hartshorn and oil bottle?

Then there are the essential or volatile oils,
found in various parts of plants; in the flowers
of some—as the orange-flower (neroli), the dried
clove-bud (essential oil of cloves), the elderflower,
lavender-spikes, rose-leaves (attar or otto
of roses), jessamine, mignonette, camomile, and
indeed in all sweet or strong-smelling flowers;
in the fruit of others—as the oil of bergamot from
the ripe fruit of the Citrus bergamia, the oil of
nutmegs (not the butter), extracted from the
mace which is the inner lining of the nutmeg, from
juniper-berries, orange rinds, and lemon rinds;
in the bark of others—as oil of cinnamon from
the bark of the cinnamon-tree of Ceylon (Laurus
cinnamomum), oil of turpentine, distilled from the
"oleo resin" of pine-trees, and when rectified and
redistilled, sold as the camphine which smokes
so abominably when not sufficiently supplied
with air, and which smokes more abominably
still when it has been left exposed to the air,
by which it becomes resinified again, and unfit
for burning; in the leaves—from orange-leaves,
from the dry leaves of the Melaleuca cajeputi,
known as cajeput oil from the Moluccas, oil of
savine, from the leaves of the Juniperus sabinus,
and others; in the seeds of many, and in the
roots of a few. But the essential oils have a
less varied usefulness than, the fatty; and if a
law was passed prohibiting the use of perfumes,
there would then be very few distilled at all.
But all are not distilled; for the essential oil of
certain flowers, in which resides the perfume,
or what chemists call the "odoriferous principle,"
is so delicate and evanescent that the
only way to get at it is by imprisoning it in a
neutral medium, as in the process called
enfleurage. Scented buds and petals are gently laid
in perfectly inodorous grease, which thus
becomes impregnated with the perfume.

Oil has a peculiar facility for developing heat.
If hemp, or wool, or paper, sawdust, rags, soot,
shavings—what not of refuse—be smeared with
oil and left to the free action of the sun and
air, they will soon get hot, begin to smoke, and
finally burst into flame: which accounts for
many of the apparently mysterious fires of mills
and manufactories. And if linseed oil and
ground maganese are "triturated" together, the
soft lump so formed will speedily become firm,
and take fire of its own accord. Oils are
purified by sulphuric acid, by steam and hot air.
passing through them, and by tannic acid. Mineral
oils, so called, are not oils at all, according
to the proper definition of oils; they are fluid
hydro-carbons, with the addition, in the Burmese
naphtha, of a considerable quantity of paraffine.

            THE UNCOMMERCIAL TRAVELLER,
             A New Series of Occasional Papers
                     By CHARLES DICKENS,
              WILL BE CONTINUED NEXT WEEK.

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