[Illustration: Diagram of apparatus as described in text]
Let there be a vessel containing wine and provided with a spout,
underneath which a goblet is placed: whatever quantity of wine is
taken from the goblet, as much shall flow into it from the spout. Let
A B (fig. 67), be the vessel of wine, and C D the spout, to which are
attached the valve E F, and the rods G H, K L, K O, L M as before; and
beneath the spout place the cup P. To the rod K O fix a small basin R
contained in the vessel S T, and let a tube, U Q, connect the vessels S
T and P. When these arrangements are complete, if the vessels S T and
P are empty, the basin R will fall to the bottom of S T, and open the
spout C D. A stream will flow from C D into both the vessels S T and P,
so that the basin will rise and shut the spout again, until we remove
more liquid from the goblet. This result will happen as often as we
remove liquid from P.
68. _A Shrine over which a Bird may be made to revolve and sing by
Worshippers turning a Wheel._
[Illustration: Diagram of apparatus as described in text]
The construction of a shrine provided with a revolving wheel of bronze,
termed a purifier, which worshippers are accustomed to turn round as
they enter. Let it be required that, if the wheel is turned, the note
of the black-cap shall be produced, and the bird, standing on the top
of the shrine, turn round as well; while, if the wheel is turned [in
the opposite direction], the black-cap neither sings nor revolves.
Let A B C D (fig. 68), be the shrine and E F an axis extending across
it, capable of revolving freely, to which the wheel H K, which is to
be turned round, is attached. Let two other wheels be attached to
the axis, in the interior of the shrine, L and M, of which L has a
pulley, and M is a wheel with rays. Round the pulley a cord is wound,
from the extremity of which is suspended a vessel N, shaped like a
conical oven, and provided with a tube X O, terminating in a small pipe
which produces the note of a black-cap: under the conical vessel N
must be placed a vessel of water. From the top of the shrine let fall
a small axis S T capable of revolving freely: at the extremity S let
a black-cap be placed, and at T a wheel with rays, the rays of which
are implicated with, or take into, the rays of the wheel M. It will be
found that, when the wheel H K is made to revolve, the cord is wound
round the pulley and raises the conical vessel N; but, if the wheel is
let go, N descends by its own weight into the water and produces the
sound by the expulsion of the air. The black-cap turns round at the
same time owing to the revolution of the wheels.
69. _A Siphon fixed in a Vessel from which the Discharge shall cease at
will._
[Illustration: Diagram of apparatus as described in text]
There are certain siphons which, when placed in vessels, flow until
the vessels are emptied, or the surface of the water has sunk to the
level of the outer orifice of the siphon. Let it be required that the
discharge shall suddenly cease whenever we wish. A B (fig. 69), is
a vessel containing a siphon, C D E, the inner leg of which is bent
upwards as at C F G. Let a vertical rod H K be fixed, on which another,
L M, works as a lever-beam: from L M extends another rod, M N, moving
on a pivot, and provided at the extremity N with a vessel large enough
to encircle the bent portion of the siphon F G. On the rod L M suspend
a weight at L, so that the encircling vessel is raised above the upward
bend of the siphon, and the siphon flows. When we wish the discharge to
cease, we have only to remove the weight at L, and the vessel at N will
descend and encircle the bend G C, so that the siphon will cease to
flow. If it is desired that the stream should continue, we must again
suspend the weight.