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_.

* * * * *




THE WATER CLOCK.


_To the Editor of the Scientific American_:

Referring to the clepsydra, or water clock, described and illustrated in
the SCIENTIFIC AMERICAN SUPPLEMENT of December 20, 1884, it strikes me
that the ingenious principle embodied in that interesting device could be
put into a shape more modern and practical, doing away with some of its
defects and insuring a greater degree of accuracy.