[Illustration: Diagram of apparatus as described in text]
The instrument called a pyulcus acts on the same principle. A hollow
tube, of some length, is made, A B (fig. 57); into this another tube,
C D, is nicely fitted, to the extremity C of which is fastened a small
plate or piston, and at D is a handle, E F. Cover the orifice A of the
tube A B with a plate in which an extremely fine tube, G H, is fixed,
its bore communicating with A B through the plate. When we desire to
draw forth any pus we must apply the extreme orifice of the small
tube, H, to the part in which the matter is, and draw the tube C D
outwards by means of the handle. As a vacuum is thus produced in A B
something else must enter to fill it, and as there is no other passage
but through the mouth of the small tube, we shall of necessity draw
up through this any fluid that may be near. Again, when we wish to
inject any liquid, we place it in the tube A B, and, taking hold of E
F, depress the tube C D, and force down the liquid until we think the
injection is effected.
58. _A Vessel from which a Flow of Wine can be stopped, by pouring into
it a small Measure of Water._
[Illustration: Diagram of apparatus as described in text]
If there be a vessel full of wine and provided with a running spout,
when a cyathus, or small measure, of water is poured upon the neck of
the vessel, the discharge of wine shall cease, but, if a second measure
of water is poured on, this last shall flow out with the former, or
the two measures of water shall flow out through two different spouts;
and, after all the water is drawn off, the wine shall flow again from
the centre spout: moreover, this shall happen as often as any liquid
is poured on and flows out. Let A B (fig. 58), be a vessel with a
spout, C, at the bottom, and closed at the neck by the partition D E
from which extends a tube, F G, encircled by another tube which is
sufficiently removed from the partition to allow of the passage of
water, as in the case of the inclosed diabetes. Through the partition
insert another tube, H K, projecting to a less height above the
partition than the former tube, and branching off below into two
spouts L and M; and let this tube also be encircled by another tube
distant a small space from the partition: furthermore let the vessel
have a vent N just under the partition. Now, if, after closing the
spouts, we pour in the wine, it will pass into the body of the vessel
through the tube F G, for the air will escape through the vent N: but
when we close the vent and set the spouts free, the liquid intercepted
in the tube H K will flow through L and M, and that contained in the
vessel through C. If, however, while C is still running, we pour a
small measure of water upon the partition, the air will no longer be
able to enter through F G, and the discharge through C will cease: but
if a second measure is poured on, the water will rise above the tube
H K, and be carried through into the spouts L and M, the whole being
drawn up; and then, the tube F G being opened to the air will enable
the spout C to flow as before. This result will take place as often as
we pour on the measures of water.
59. _A Vessel from which Wine or Water may be made to flow, separately
or mixed._
[Illustration: Diagram of apparatus as described in text]
From a vessel full of pure wine sometimes the wine flows; if water is
poured in, pure water flows out; then again pure wine; and, if it is
desired, when the water is poured in a mixture shall be discharged.
Let A B (fig. 59), be a vessel, having a partition near the neck,
C D, through which a tube, E F, is inserted, passing out below and
terminating in a spout. In the tube E F, within the vessel and near
the bottom at G, let there be a fine hole, and a vent under the neck
at H. Now, if we close the spout F, and pour in the wine, it will pass
into the body of the vessel, the air escaping through the vent H: but
if we stop the vent and set the spout free, nothing will flow out
except what is intercepted in the tube E F. If water is then poured in,
it will flow out pure, and, when the vent is set free, a mixture is
discharged: if nothing more is poured in, pure wine will flow.
60. _Libations poured on an Altar, and a Serpent made to hiss, by the
Action of Fire._
[Illustration: Diagram of apparatus as described in text]
When a fire is kindled on an altar, figures placed near shall offer
libations, and a serpent hiss. Let there be a hollow pedestal, A B
(fig. 60), on which is an altar, C, containing within it a tube, D E,
which descends from the hearth of the altar to the pedestal, and then
branches off into three tubes, E F leading to the mouth of the serpent;
E G H to a wine vessel K L, (the bottom of which must be higher than
the figure M,) and fastened to the lid of K L cross-bar fashion; while
the other tube E N X, in like manner, extends into another wine
vessel O P, also terminating in a cross-head. Both these tubes must
be soldered into the bottoms of the vessels, and in each wine vessel
there must be a bent siphon, R S, and T U, one extremity of each being
immersed in the wine, and the other, (from which extend the hand
of the figure which is to pour the libation,) passing, air-tight,
through the side of the wine vessel. When the fire is about to be
kindled, pour first a little water into the tubes, that they may not
be burst by the dry heat, and close up everything that no air may pass
through. The hot air, becoming mixed with the water, will ascend along
the tubes to the cross-heads, and through them it will exert pressure
on the wine, and carry it to the bent siphons R S and T U. The wine
flowing through the hands of the figures produces a libation as long as
a fire is burning on the altar. The other tube, conveying the hot air
to the mouth of the serpent, will cause the serpent to hiss.
61. _Water flowing from a Siphon ceases on surrounding the End of its
longer Side with Water._
[Illustration: Diagram of apparatus as described in text]
Let there be an air-tight vessel provided with an open spout, and by
its side a thyrsus under which is a cup full of water: if the cup is
removed, as long as it is withdrawn, a small stream shall flow from
the mouth; but when the cup is pushed back, the spout shall run no
longer. Let A B (fig. 61), be the vessel described, having its neck
closed by the partition C D; from C D, and fitted air-tight in it, a
tube, E F, extends, about which lies another tube, K L, forming an
inclosed diabetes. With K L another tube, M N, communicates, of which
the mouth M is open, while the outer leg is placed in a cup, O X, into
which water has been poured until it is full; it is clear that so much
of the leg of the siphon as is in the cup will be filled at the same
time. Into the neck of the vessel A B a little water must be poured,
just enough to close all entrance for the air; and, when A B is full,
the spout P, though open, will not run, since the air has no means of
entrance, because of the water poured into the neck. But if the cup
is drawn slightly downwards, some portion of the leg of the siphon
which is in the cup must be emptied, and into the part emptied the
contiguous air will be drawn: this air will attract some of the water
which was poured into the neck, so that the water shall rise above
the mouth F; and hence, the air having found an entrance, the spout P
will run until the cup O X is pushed up again, causing the water to
return to its old position and to close the passage for the air so that
the spout will cease to flow. This will happen as often as the cup is
withdrawn and applied: it is necessary however that the cup be not
wholly drawn away, that the siphon leg may not be wholly emptied. Let
the tube M N be fashioned like a thyrsus, R N being its shaft: thus the
spectacle will be properly arranged.