the figure of a truncated pyramid, of eight
inches high. Cover it with a glass, or rather a board, in which are
placed two lenses, O, of eight inches focus, and distant from each
other about half an inch. Line the four plates of glass that compose
the sides with very thin paper, that will admit the light, and at the
same time prevent the company from seeing the circles on the board.

These preparations being made, you give the box to any one, and tell
him to place the tablets, on which the words are written privately, in
what position he thinks proper, then to close the box, and, if he
please, to wrap it up in paper, seal it, and give it to you. Then
placing the board with the pyramid upon it, you immediately tell him
the order in which the tablets are placed, by reading the words to
which the needles on the circles point.

INTERESTING EXPERIMENTS WITH THE AIR-PUMP.

We shall not occupy the time of our readers by describing the form and
nature of the air-pump; since those persons whose circumstances will
enable them to have it, can purchase it properly made at an
optician's, at less expense, and with far less trouble, than they can
construct, or cause it to be constructed, themselves.

_Bottles broken by Air._

Take a square bottle of thin glass, and of any size. Apply it to the
hole of the air-pump, and exhaust the air. The bottle will sustain the
weight of the external air as long as it is able, but at length it
will suddenly burst into very small particles, and with a loud
explosion.

An opposite effect will be produced, if the mouth of a bottle be
sealed so close that no air can escape; then place it in the receiver,
and exhaust the air from its surface. The air which is confined within
the bottle, when the external air is drawn off, will act so powerfully
as to break the bottle into pieces.

_Glass broken by Air._

Lay a square of glass on the top of an open receiver, and exhaust the
air. The weight of the external air will press on the glass, and smash
it to atoms.

_The Hand fixed by Air._

If a person hold his hand on an open receiver, and the air be
exhausted, it will be fixed as if pressed by a weight of sixty pounds.

_Water boiled by Air._

Take water made so warm that you can just bear your hand in it, but
that has not been boiled; put it under the receiver, and exhaust the
air. Bubbles of air will soon be seen to rise, at first very small,
but presently become larger, and