Section 4
No. 4. Siphon which is capable of discharging a greater or less
quality of Liquid with uniformity.
BY the following arrangement we can produce a discharge at once uniform
and variable; that is a discharge in which for a certain time at
pleasure, the stream continues uniform from the beginning, and again,
for any other period, is slower or quicker than before, but still
uniform with itself. As before, let A B (fig. 4.) be a vessel of water,
and C D a basin. Into the lid and bottom of the basin solder a tube L M
wider than the inner leg of the siphon. On the lid place a wooden
frame, C N X D, consisting of two upright pieces and a third lying
across them on the top. In the inner sides of the upright pieces let
grooves be cut down their whole length, along which another piece 0 P iS to
move freely. Let R S be a screw, working perpendicularly in the
direction of the lid C D, and passing ~rough a hole in 0 P: in 0 P let a
pin be so fixed as to enter the spiral thread of the screw. The screw
must project above N X, and a handle be fastened to its top by which to
turn it, and by this means O P can be raised or lowered. Let the inner
leg of the siphon be fixed in O P, and pass through the tube L M, so
that its mouth may dip into the water in the vessel. 
Now if, as before, we draw off the liquid
through the outer mouth, the siphon will flow with a uniform stream
until the whole be exhausted. And when it is wished that a quicker
stream should be produced through the siphon, but uniform with itself,
let the screw be turned so as to lower the board 0 P; for then the
excess of the outer leg is increased, and thus the stream is still of
uniform velocity, but quicker than before. If a still greater velocity
is desired, turn the screw so as to lower 0 P still further ; and if a
less velocity is sought, let 0 P be raised. Thus a discharge is
produced through a siphon in one sense uniform, in another variable.
Section 5.
Index.