"The principle of lateral pressure may now be strikingly
illustrated by taking an American wooden pail and, having
previously cut a large circular hole in the bottom, this is now
covered with fine tissue paper, which should be carefully pasted on
to prevent the particles of sand from flowing through the small
openings between the paper and the wood * * * and being placed
upright and rapidly filled with sand, it may be carried about by
the handle without the slightest fear of the weight of the sand
breaking through the thin medium. * * *

"Probably one of the most convincing experiments is that which may
be performed with a cylindrical tube 18 in. long and 2 in. in
diameter, open at both ends. A piece of tissue paper is carefully
pasted on one end, so that when dry no cracks or interstices are
left. The tube is filled with dry sand to a height of say 12 in. In
the upper part is inserted a solid plug of wood 12 in. long and of
the same or very nearly the same diameter as the inside of the
tube, so that it will move freely up and down like the piston of an
air pump. The tube, sand, and piston being arranged as described,
may now be held by an assistant and the demonstrator, taking a
sledge hammer, may proceed to strike steadily on the end of the
piston and, although the paper will bulge out a little, the force
of the blow will not break it.

"If the assistant holding the tube allows it to jerk or rebound
after each blow of the hammer, the paper may break, because air and
sand are driven down by the succeeding blow, and therefore it must
be held steadily so that the piston bears fairly on the sand each
time.