small quantity of this out of the phial into the cool air, and
it will immediately take fire, but will not burn any thing. Keep the
bottle dry, as even the air will spoil it effectually.

_The Magical Mirrors._

Make two holes in the wainscot of a room, each a foot high and ten
inches wide, and about a foot distant from each other. Let these
apertures be about the height of a man's head, and in each of them
place a transparent glass in a frame, like a common mirror.

Behind the partition, and directly facing each aperture, place two
mirrors enclosed in the wainscot, in an angle of forty-five
degrees.[B] These mirrors are each to be eighteen inches square: and
all the space between them must be enclosed with pasteboard painted
black, and well closed, that no light can enter; let there be also two
curtains to cover them, which you may draw aside at pleasure.

When a person looks into one of these fictitious mirrors, instead of
seeing his own face he will see the object that is in front of the
other; thus, if two persons stand at the same time before these
mirrors, instead of each seeing himself; they will reciprocally see
each other.

There should be a sconce with a lighted candle, placed on each side of
the two glasses in the wainscot, to enlighten the faces of the persons
who look in them, or the experiment will not have so remarkable an
effect.

[B] That is, half-way between a line drawn perpendicularly to
the ground and its surface.

_To cause a brilliant Explosion under Water._

Drop a piece of phosphorus, the size of a pea, into a tumbler of hot
water; and, from a bladder furnished with a stop-cock, force a stream
of oxygen directly upon it. This will afford a most brilliant
combustion under water.

_Fulminating Mercury._

Dissolve 100 grains of mercury by heat, in an ounce and a half of
nitric acid. This solution being poured cold upon two measured ounces
of alcohol previously introduced into any convenient glass vessel, a
moderate heat is to be applied, till effervescence is excited. A white
fume then begins to appear on the surface of the liquor, and the
powder will be gradually precipitated when the action ceases. The
precipitate is to be immediately collected on a filter, well washed
with distilled water, and cautiously dried in a heat not exceeding
that of a water-bath. Washing the powder immediately is material,
because it is liable to the re-action of the nitric acid; and, while
a