or more tubes be immersed in the same
fluid, the one with a narrow canal, and the other wider, the water
will ascend higher in the former than the latter.

_The Magician's Mirror._

Construct a box of wood, of a cubical shape, A B C D, Fig. 23, of
about fifteen inches every way. Let it be fixed to the pedestal P, at
the usual height of a man's head. In each side of this box let there
be an opening, of an oval form, ten inches high, and seven wide. In
this box place two mirrors, A D, with their backs against each other.
Let them cross the box in a diagonal line, and in a vertical position.
Decorate the openings in the side of this box with four oval frames
and transparent glasses, and cover each with a curtain so contrived as
all to draw up together.

[Illustration: Fig. 23.]

Place four persons in front of the four sides, and at equal distances
from the box, and then draw them up that they may see themselves in
the mirrors, when each of them, instead of his own figure, will see
that of the person next to him, but who will appear to him to be
placed on the opposite side. Their confusion will be the greater, as
it will be very difficult, if not impossible, for them to discover the
mirrors concealed in the box. The reason of this phenomenon is
evident; for though the rays of light may be turned aside by a mirror,
yet they always _appear_ to proceed in right lines.

_The Perspective Mirror._

Provide a box, A B C D, Fig. 24, of about two feet long, 15 inches
wide, and 12 inches high. At the end A C, place the concave mirror,
the focus of whose parallel rays is 18 inches from the reflecting
surface. At I L place a pasteboard, blacked, in which a hole is cut,
sufficiently large to see on the mirror H the object placed at B E F
D. Cover the top of the box, from A to I, close, that the mirror H may
be entirely darkened. The other part, I B, must be covered with glass,
under which is placed a gauze, or oiled paper, to prevent the inside
from being seen. Make an aperture at G, near the top of the side E B,
beneath which, on the inside, place in succession, paintings of
vistas, landscapes, figures, &c., so that they may be in front of the
mirror H. Let the box be placed that the objects may be strongly
illuminated by the sun, or by wax-lights placed under the enclosed
part of the box A I. By this simple construction, the objects placed
at G D will be thrown into their natural perspective, and if the
subjects be proper