[Illustration: Diagram of apparatus as described in text]
The construction of a lamp. * * * * * * * * Underneath the lamp place
a vessel perfectly air-tight, A B (fig. 73), either attached to the
lamp or distinct from it. From this let two tubes extend, C D, E F,
communicating with the vessel; the extremity C must reach to the bottom
except a space sufficient for the passage of water, and the tube C D to
the surface of the lamp, having at the extremity D a small cup through
which the water is to be poured in: the tube E F must pass, air-tight,
through the bottom of the lamp. Now if oil be poured through the
opening, it will first pass into the vessel A B, and then, when A B is
full, the tubes C D, E F, and the lamp will be filled also. As the lamp
burns it will become empty, and if we pour in water through the cup,
it will pass into the vessel A B, and the oil will ascend and fill up
the deficiency in the lamp, until it reaches the lamp-nozzle. When the
oil has sunk again, we must do the same, repeating it till the supply
is expended. If it is required to remove the vessel A B, the oil being
retained in the lamp, there must be a valve or tap in the pipes C D, E
F, close to the vessel A B, with keys near the lamp, so that when the
keys are turned, the oil in the lamp, and that in the tubes, shall be
confined. Thus the vessel may be removed from the lamp, and, whenever
it is desired, we may bring them together again, and open the keys. It
is better that the pipe E F should lead to the handle of the lamp, and
C D a little behind it, having the cup which communicates with it, and
through which water will be poured in, placed above; so that the oil
will flow from the handle at the same time that the water is poured
into the cup.
74. _A Steam-Boiler from which a hot-Air blast, or hot-Air mixed with
Steam is blown into the Fire, and from which hot water flows on the
introduction of cold._
[Illustration: Diagram of apparatus as described in text]
The construction of a boiler, on which if a figure is placed, shaped as
if in the act of blowing, the figure shall blow on the coals and thus
the boiler be heated: moreover, if an open spout project near the mouth
of the boiler, nothing shall flow from it until we have first poured
cold water into a cup; and the cold water shall not mix with the hot
until it passes to the bottom of the vessel, while water extremely hot
flows from the spout. The shape of the boiler having been determined
at pleasure, in that part of it intended to hold the water a small
chamber, perfectly air-tight, is intercepted between two perpendicular
partitions. With this chamber a tube, one of those which pass under
the coals, communicates near the bottom, one end of the tube being
closed that no water may enter it from the boiler: the other tubes lead
into the chamber where the water is. Thus when the coals are ignited
they will generate vapour through that tube which leads into the small
chamber. This vapour is carried along a tube which pierces the surface
of the boiler, and through the mouth of the figure on to the coals,
(for the figure must be bent so as to blow downwards;) and as vapour
is always being generated, the figure is always blowing. The vapour is
generated from the fire, and, if we pour a very small quantity of water
into the small chamber, we shall produce more vapour, and the figure,
blowing with great violence, will heat the boiler still higher: just as
in the case of cauldrons exposed to fire we see smoke ascending from
the water. The figure should be moveable by means of a double sliding
tube, to allow of our pouring in the small quantity of water: and,
at the same time, by means of this tube, whenever we do not require
the figure to blow on the coals, we can turn it round in the opposite
direction. On the surface place a small cup from which a tube leads to
the bottom of the boiler, that when cold water is poured in, it may
pass through to the bottom. In order that the boiler may admit of being
filled when water is poured in, and, at the same time, that the water
may not boil over and run out, let another pipe communicate with the
cup on its inner surface, to avoid offending the sight. We will now
expose to view the construction of the boiler. Set up a hollow cylinder
(fig. 74), of which A B is the under surface, and C D the upper; and
construct another hollow cylinder, with the same axis as the former, of
which E F is the under surface, and G H the upper. On the outer edges
of the cylinders let plates be fastened, so as to keep the cylinders
together and cover the edges. In the cylinder E F G H place the tubes,
O K, L X, M N, of which L X perforates the cylinder on one side only at
X, while the other two are bored quite through at each end, and their
orifices either way open into the space between the cylinders. Into the
space intercepted between the two cylinders let down the partitions E
G, H F, intercepting the chamber G H E F, into which the tube described
above, perforated at one side only, penetrates. Place on the surface,
that is on G H, a small tube having the figure attached to, and
communicating with, it; the figure must be perforated throughout, and
incline downwards so as to look towards the coals. That the figure may
cease blowing whenever we like, let the tube on which it sits be fitted
tightly into the other, so that, when we turn it round in the opposite
direction, the figure will no longer blow on the coals but away from
the boiler. We shall also find this sliding tube useful for pouring
water into the chamber G F E H, for, after raising the figure from the
tube on which it is placed, we can pour the water through, and thus
more vapour will be passed along into the figure. On the surface H C
let a cup, R S, be placed; communicating with the interior, and having
a tube at its extremity reaching down to the bottom of the boiler with
the exception of a passage for water. When we desire to let the hot
water out, we must pour in cold through R S; this will pass through
the tube which communicates with the cup into the chamber of the warm
water, which will ascend and flow out through the spout near the neck,
for the cold water which has been introduced will not yet have mingled
with the warm below. As often as this is repeated we shall obtain
warm water for the cold we throw in. In order that we may know when
the boiler will bubble up, the _chasmatium_ is contrived, perforated
throughout, and placed on the neck, a hole having been made in the
surface: it is furnished with a small tube which looks towards the cup
R S, that, when the warm water ascends, it may be carried into the cup.
Such is the construction of the boiler. If we prefer not to cut off the
chamber F G E H through the whole length, but only for a portion of
it, the partitions are made to reach half-way, and another is placed
upon them, admitting through it a tube which extends up to the figure.
When the fire is kindled there will be a rush of vapour from the small
chamber, into which water will be poured as before.
75. _A Steam-Boiler from which either a hot Blast may be driven into
the Fire, a Blackbird made to sing, or a Triton to blow a Horn._
[Illustration: Diagram of apparatus as described in text]
Another construction of the same kind is employed to produce the sound
of a trumpet and the note of a blackbird. A boiler is made (fig. 75),
of the same kind as the last, of which all the tubes in the base
are bored through at each end, and near the surface there is a tube
Q E, into which another tube K L is closely fitted, extending into
the chamber for warm air, and moveable about the pin K L. This tube
is perforated by three holes, M, N, X, and similarly three
holes are bored in Q E opposite the holes M, N, X. Near
X, an aperture is made in a support which receives a tube fitting
closely into X and surmounted by the figure, as was described in the
last paragraph: and from M and N two tubes extend, M O, N P, bent at
their upper extremities; these tubes pierce through the surface of the
boiler, into which they are carefully soldered. Through the apertures
other tubes pass, fitting tightly into the tubes P and O. On one of
these tubes is placed the figure of a sparrow, hollow within so as to
receive water: the tube on which the bird sits is bent, and provided
with a tuning-pipe, such as are made to produce notes, and the curved
part of it passes as far as the water contained in the sparrow, so
that, when the sound of the pipe reaches the water, the note of a
blackbird is produced. In like manner the tube N P has another tube
fitting closely into it, on which is placed a figure shaped like a
triton with a trumpet in its mouth: the tube on which the triton is
placed is moreover furnished with the mouthpiece and bell as usual,
and when the vapour reaches these and enters them it will give out the
sound of a trumpet. We must discover by trial when the holes in K L are
opposite the tubes M O and N P, and when to X on which the figure is
placed. Having learnt this, we must make corresponding marks on the pin
K L, that the trumpet may sound, or the figure blow, or the blackbird’s
note be produced, at our pleasure. The arrangements about the cup and
the ascent of the warm water are to be made according to the previous
description.