If a glass tube about three feet in length, provided at its upper
extremity with a valve that opens outwardly, and at its lower with one
that opens inwardly, be dipped into water and given a series of up and
down motions, the water will be seen to quickly rise therein and finally
spurt out at the top. The explanation of the phenomenon is very simple.
Upon immersing the tube in the water it fills as far as to the external
level of the liquid, and the air is expelled from the interior. If the
tube be suddenly raised without removing its lower extremity from the
water, the valve will close, the water will rise with the tube, and,
through the velocity it has acquired, will ascend far above its preceding
level. Now, upon repeating the up and down motion of the tube in the water
five or six times, the tube will be filled, and will expel the liquid
every time that the vertical motion occurs.
[Illustration: THE CHINESE PUMP.]
We speak here of a _glass_ tube, because with this the phenomenon may be
observed. Any tube, of course, would produce the same results.
The manufacture of the apparatus is very simple. The tube is closed above
or below, according to the system one desires to adopt, by means of a
perforated cork. The valve is made of a piece of kid skin, which is fixed
by means of a bent pin and a brass wire (Fig. 2). It is necessary to wet
the skin in order that it may work properly and form a hermetic valve. The
arrangement of the lower valve necessitates the use of a tube of
considerable diameter (Fig. 1). We would advise the adoption of the
arrangement shown in Fig. 2. Under such circumstances a tube half an inch
in diameter and about 3 feet in length will answer very well.
It is better yet to simply use one's forefinger. The tube is taken in the
right hand, as shown in Fig. 3, and the forefinger placed over the
aperture. The finger should be wetted in order to perfect its adherence,
and should not be pressed too hard against the mouth of the tube. It is
only necessary to plunge the apparatus a few inches into the liquid and
work it rapidly up and down, when the water will rise therein at every
motion and spurt out of the top.
This is an easy way of constructing the _Chinese Pump_, which is found
described in treatises upon hydraulics. Such a pump could not, of course,
be economically used in practice on account of the friction of the column
of water against a wide surface in the interior of the tube. It is
necessary to consider the pistonless pump for what it is worth--an
interesting experimental apparatus that any one can make for himself.--_La
Nature_.
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