rays to diverge more, and converging rays to converge less--they
represent objects smaller than they really are--because the angle
formed by the reflected ray is rendered more acute by a convex than by
a plane surface, and it is the diminishing of the visual angle, by
causing rays of light to be farther extended before they meet in a
point, which produces the image of convex mirrors. The greater the
convexity of a mirror, the more will the images of the objects be
diminished, and the nearer will they appear to the surface. These
mirrors furnish science with many curious and pleasing facts.

Concave mirrors are the reverse of convex; the latter being rounded
outwards, the former hollowed inwards--they render rays of light more
converging--collect rays instead of dispersing them, and magnify
objects while the convex diminishes them.

Rays of light may be collected in the focus of a mirror to such
intensity as to melt metals. The ordinary burning glass is an
illustration of this fact; although the rays of light are refracted, or
passed through the glass and concentrated into a focus beneath.

When incident rays are parallel, the reflected rays converge to a
focus, but when the incident rays proceed from a focus, or are
divergent, they are reflected parallel. It is only when an object is
nearer to a concave mirror than its centre of concavity, that its image
is magnified; for when the object is farther from the mirror, this
centre will appear less than the object, and in an inverted position.

The centre of concavity in a concave mirror, is an imaginary point
placed in the centre of a circle formed by continuing the boundary of
the concavity of the mirror from any one point of the edge to another
parallel to and beneath it.

REFRACTION OF LIGHT:--I now pass to the consideration of the passage of
light through bodies.

A ray of light failing perpendicularly through the air upon a surface
of glass or water passes on in a straight line through the body; but if
it, in passing from one medium to another of different density, fall
obliquely, it is bent from its direct course and recedes from it,
either towards the right or left, and this bending is called
refraction; (see Fig. 3, b.) If a ray of light passes from a rarer into
a denser medium it is refracted towards a perpendicular in that medium;
but if it passes from a denser into rarer it is bent further from a
perpendicular in that medium. Owing to this bending of