dotted
lines on the plane, on the surface of the mirror, and also on the
reflection.

[Illustration: Fig. 300.]

CLXIX

THE UPRIGHT MIRROR AT AN ANGLE OF 45 DEG. TO THE WALL

In Fig. 301 the mirror is vertical and at an angle of 45 deg to the wall
opposite the spectator, so that it reflects a portion of that wall as
though it were receding from us at right angles; and the wall with the
pictures upon it, which appears to be facing us, in reality is on our
left.

[Illustration: Fig. 301.]

An endless number of complicated problems could be invented of the
inclined mirror, but they would be mere puzzles calculated rather to
deter the student than to instruct him. What we chiefly have to bear in
mind is the simple principle of reflections. When a mirror is vertical
and placed at the end or side of a room it reflects that room and gives
the impression that we are in one double the size. If two mirrors are
placed opposite to each other at each end of a room they reflect and
reflect, so that we see an endless number of rooms.

Again, if we are sitting in a gallery of pictures with a hand mirror,
we can so turn and twist that mirror about that we can bring any picture
in front of us, whether it is behind us, at the side, or even on the
ceiling. Indeed, when one goes to those old palaces and churches where
pictures are painted on the ceiling, as in the Sistine Chapel or the
Louvre, or the palaces at Venice, it is not a bad plan to take a hand
mirror with us, so that we can see those elevated works of art in
comfort.

There are also many uses for the mirror in the studio, well known to the
artist. One is to look at one's own picture reversed, when faults become
more evident; and another, when the model is required to be at a longer
distance than the dimensions of the studio will admit, by drawing his
reflection in the glass we double the distance he is from us.

The reason the mirror shows the fault of a work to which the eye has
become accustomed is that it doubles it. Thus if a line that should be
vertical is leaning to one side, in the mirror it will lean to the
other; so that if it is out of the perpendicular to the left, its
reflection will be out of the perpendicular to the right, making a
double divergence from one to the other.

CLXX

MENTAL PERSPECTIVE

Before we part, I should like to say a word about mental perspective,
for we must remember that some see farther than others, and som