The Sun.
London, England, 1861-01-04 00:00:00

ROYAL INSTITUTION.

The Christmas course of lectures by Professor
Faraday on the " Chemical History of a Candle,"
have proved highly attractive on every occasion,
and yesterday, when the fourth was delivered, the
hall was as on former occasions crowded, a very
large number of the audience consisting of
juveniles, for whom the explanations of Mr. Fara-
day are more particularly intended. The professor
has already explained, in the course of his first
three lectures, that the flame of a candle is merely
a shell of luminous particles, though when burning
steadily it appears as a solid mass—of this fact ar,
illnstratioß was given by holding a piece of parker
for a Moment in the centre of the flame, vihich
sco':ched a ring in the upper surface of the par,er. Im-
mediately above the wick of a candle, when,
a dark part is observed where the vapour which
causes the luminosity of the flaw) is collected
before it is burned, and by means of a bent tube,
one end of which was introduced. into the centre of
the flame this vapour was drawn off and burned at
the end some distance from the candle ; by the ap-
plication of the tube to the other parts of the flame
the products were collected in the like manner, thus
showing the different conditions of various portions
of the flame; when the products just above the
flame were collected and a lighted taper was intro-
duced into the vessel it was extinguished. With a
view to the' exemplification of the principle on
which the luminosity of the flame depends, the
lecturer first exploded some gunpowder with
which iron filings were mingled, the bright
incandescence of the sparks produced illustrating
the mode by which a jet of hydrogen gas, though
of itself not luminous, becomes very brilliant
when solid particles are introduced into it. In such
cases the particles introduced may be merely ren-
dered incandescent without being consumed, as
when lime is introduced into the flame of oxygen
and hydrogen gases, by which means the lime or
Drummond light is produced. In other cases it
was shown that the particles underwent combus-
tion, as in the flame of a candle, by the combustion
of the carbon of the tallow. To show the large
quantity of carbon, or charcoal, contained in com-
bustible substances that afford the most light,
some cotton dipped in turpentine was lighted ;
the smoke arising therefrom, when burned
in an open vessel, is most offensive, but when
properly collected in a lamp made for the purpose
burns beautifully and brightly. Amongst many
other experiments, that of throwing lycopodium
on a flame, and thus producing a bright flash,
proved highly amusing to the youngsters who
were present. The next stage in the chemical his-
tory of a candle to which the lecturer referred was
the production of water by combustion ; pure water
was produced from gas by the process of combus-
tion, and a pint of oil when fairly treated by this
process was shown to produce a pint of water.
In the like manner water was produced by placing
a candle under a ladle cooled by having ice and salt
placed:in its bowl. The expansion of water, when
subjected to heat, was shown by putting sufficient
water into a tin can to cover the bottom to a
depth of half an inch, when, .by placing a spirit
lamp under it, the can was filled with steam,
the stop cock was closed to prevent the escape
of the steam, and it was reconverted into
water by suddenly being condensed, and a
vacuum being produced, the can collapsed ;
thus establishing the fact which Mr. Fara-
day had stated as to the expansion of water sub-
jected to heat. Cold was shown to have a similar
effect. A small drop of water was put into a
cast-iron bottle and screwed down. It was then

frozen by artificial means; and although the
iron was half an inch thick the bottle was
burst by the pressure of the ice from within.
The water produced from the lighted candle he
explained was the product of the combined action
of the air and the candle. The power, or rather
the lightness, of hydrogen was shown in raising
balloons, and the electric light was produced by
means of a Voltaic battery with 40 sets of plates,
The topics of the address yesterday were oxygen,
the atmosphere, and hydrogen. Mr. Faraday said
he had explained the existence of hydrogen in the
water produced from the burning of a candle on
the last occasion, and he now proposed to show
that the water contained some other product.
For the purpose of illustration he dissolved some
copper shavings in sulphuric and nitric acid,
and then placed two strips of platinum in the
solution so produced ; to these the poles of the
battery above slescribed were applied, and one of
them at once became coated with copper, showing
how, by the proper application of electro power,
the reproduction of the metal took place. He
then used the battery in like manner on water,
and produced oxygen and hydrogen from it. These