[Illustration: Diagram of apparatus as described in text]
The construction of a small temple such that, on lighting a fire,
the doors shall open spontaneously, and shut again when the fire is
extinguished. Let the proposed temple stand on a pedestal, A B C D
(fig. 37), on which lies a small altar, E D. Through the altar insert a
tube, F G, of which the mouth F is within the altar, and the mouth G is
contained in a globe, H, reaching nearly to its centre: the tube must
be soldered into the globe, in which a bent siphon, K L M, is placed.
Let the hinges of the doors be extended downwards and turn freely on
pivots in the base A B C D; and from the hinges let two chains, running
into one, be attached, by means of a pulley, to a hollow vessel, N X,
which is suspended; while other chains, wound upon the hinges in an
opposite direction to the former, and running into one, are attached,
by means of a pulley, to a leaden weight, on the descent of which the
doors will be shut. Let the outer leg of the siphon K L M lead into the
suspended vessel; and through a hole, P, which must be carefully closed
afterwards, pour water into the globe enough to fill one half of it. It
will be found that, when the fire has grown hot, the air in the altar
becoming heated expands into a larger space; and, passing through the
tube F G into the globe, it will drive out the liquid contained there
through the siphon K L M into the suspended vessel, which, descending
with its weight, will tighten the chains and open the doors. Again,
when the fire is extinguished, the rarefied air will escape through the
pores in the side of the globe, and the bent siphon, (the extremity of
which will be immersed in the water in the suspended vessel) will draw
up the liquid in the vessel in order to fill up the void left by the
particles removed. When the vessel is lightened the weight suspended
will preponderate and shut the doors. Some in place of water use
quicksilver, as it is heavier than water and is easily disunited by
fire.
38. _Other intermediate means of opening Temple Doors by Fire on an
Altar._
[Illustration: Diagram of apparatus as described in text]
There is another way in which, on lighting a fire, the doors will open.
As before, let a small temple stand upon a base, A B C D (fig. 38), on
which is an altar, E. Let a tube, F G H, pass through the altar and
be attached to a leathern bag, K, perfectly air-tight: beneath this
let a small weight, L, hang, from which a chain is attached across a
pulley to the chains round the hinges, so that, when the bag is folded
together, the weight L preponderates and shuts the doors, and when fire
is placed on the altar they are opened. For, as before, the air in the
altar growing hot, and expanding, will pass through the tube F G H into
the bag, and raise it up with the weight L; and then the doors will be
opened. The doors will either open of themselves, as the doors of baths
shut spontaneously, or they may have a counterbalancing weight to open
them. When the sacrifice is extinguished, and the air which has entered
the bag passes out, the weight, descending with the bag, will tighten
the chains and close the doors.
39. _Wine flowing from a Vessel may be arrested on the Introduction of
Water, but, when the Supply of Water ceases, the Wine flows again._
[Illustration: Diagram of apparatus as described in text]
If there be a vessel containing wine, and provided with three spouts,
wine shall flow through the middle of the three; and, when water is
poured in, the stream of wine shall cease, and water shall flow through
the other two; again, when the stream of water ceases, wine shall flow
through the middle spout: and this shall take place as often as we pour
in water. Let A B (fig. 39), be a vessel, the neck of which is closed
by the partition C D, and having a spout, E, at the bottom. Let two
tubes, F G H, K L M, terminating in spouts, pass through the partition
and project above it; and round the projecting parts place other tubes,
N, X, covered with lids at the top and extending to the partition
except a passage for the water. Another tube, P, reaching nearly up to
the partition, communicates with F G H. Having first closed the spout
E, fill the vessel A B with wine through an orifice, Q, which must
be carefully closed afterwards. When E is set free it will be found
that wine flows through it, for air enters from without into the void
created, through the orifice H and the tube P. Now, if we pour water
upon the partition C D, it will be carried out through the tubes F G
H, K L M; but, as the air has no means of entering the vessel A B,
the wine will cease to flow until all the water has escaped, when the
air finds an entrance again and the wine flows. Instead of the tube
P, another tube, R S, may be used, piercing through the partition,
about which another, T U, must lie, like the tubes N and X, but higher
than those, so that R S may rise above the lip of the vessel. The same
result will follow.
40. _On an Apple being lifted, Hercules shoots a Dragon which then
hisses._
[Illustration: Diagram of apparatus as described in text]
On a pedestal is placed a small tree round which a serpent or dragon
is coiled; a figure of Hercules stands near shooting from a bow, and
an apple lies upon the pedestal: if any one raises, with the hand,
the apple a little from the pedestal, Hercules shall discharge his
arrow at the serpent and the serpent hiss. Let A B (fig. 40) be the
proposed pedestal, air-tight and divided by a partition, C D. Fixed in
the partition is a hollow truncated cone, E F, the lesser circle of
which, F, is open and approaches to the bottom of the pedestal, leaving
a sufficient interval for the passage of water. To this cone must be
tightly fitted another cone H, attached by means of a chain through a
hole in the surface, to the apple K, which lies on the pedestal. Let
Hercules hold a small bow of horn, the string of which is stretched,
and at the proper distance from the hand. In the right hand, and
directed towards the serpent, let there be a hand in every respect
similar to the visible hand, but smaller, and holding the trigger. From
the extremity of the trigger let a chain, or cord, proceed through
the pedestal and be attached to a pulley, which is placed above the
partition, and again to the chain which is connected with the cone
and apple. Now we must draw the bow, and placing the trigger beneath
the hand, close it so that the cord is stretched and draws the apple
tightly downwards: the cord must run inside Hercules and through the
body and hand. From the partition let a small tube, one of those which
are used to whistle, extend above the pedestal and pass under the tree
or along its trunk. Then fill the vessel A D with water. Let L M be the
tree, N X the bow, S P the string, R S the hand that grasps the bow, T
U the trigger, Q W the cord, W the pulley round which the cord runs,
and Y Z the whistling pipe. Now if some one raise the apple K, he will
at the same time raise the cone H, tighten the cord Q W, and draw back
the hand, so that the arrow is discharged: and the water in A D, being
carried into B C, will drive out the air contained in B C through the
pipe, and produce the hissing sound. When the apple is replaced, the
cone H fitting again into the other, will stop the stream of water so
that no sound is produced. We must now re-arrange the arrow and leave
it. If the vessel B C is full, it can be emptied again by means of a
spout with a key: A D must be filled as before.
41. _A Vessel from which uniform Quantities only of Liquid can be
poured._
[Illustration: Diagram of apparatus as described in text]
The following is the construction of the vessel called a dicæometer,
which, having been filled with liquid, discharges an equal quantity
every time it is inverted. Let A B (fig. 41), be a vessel the neck
of which is closed by the partition A B: near its bottom let there
be a small globe, C, holding the measure of water we intend to flow
out. Through the partition insert a small and very fine tube, D E,
communicating with the globe. In the lower part of the globe perforate
a small hole, F, from which a pipe, F G, extends upwards, running
just beneath, and communicating with, the handle of the vessel which
is hollow. Near the hole just mentioned make another at L towards the
body of the vessel: the handle also must have a vent at H. Having first
stopped the vent H we must fill the vessel with liquid through a hole
which must afterwards be carefully closed, or the vessel may even be
filled through the tube D E itself, a fine hole, however, being made in
the body of the vessel through which the air can be driven out; and the
globe C will be filled with liquid at the same time through the tube D
E. Now, if we invert the vessel and set the vent H free, the liquid in
the globe C and the tube D E will flow out. If we again close the vent
and restore the vessel to its original position, the globe and tube
will be filled again, for the air they contain will be driven out by
the liquid rushing in; and, when the vessel is once more inverted, a
like quantity of liquid will again flow out, except indeed with some
difference as to the tube D E, for it will not be always filled, but as
the vessel grows empty it will be empty itself: this difference however
is extremely small.