m the excessive heat of the burner.

In appearance the lights may be classed as _stationary_, _revolving_,
_flashing_, and _intermittent_. In the first, as its name implies, the
light has a steady and uniform appearance, and the reflectors, which
are smaller than those used for revolving lights, are ranged in
circular zones upon a chandelier or piece of iron frame-work, with
their axes inclined at such an angle as shall enable them to
illuminate every part of the horizon. The _revolving_ light consists
of a frame built upon a perpendicular shaft, and the reflectors, which
are of large size, are ranged on perpendicular planes or faces, which
are made to revolve in periodic times, by means of a train of
machinery kept in motion by a weight. When one of those illuminated
planes or faces is brought towards the eye of the observer, the light
gradually increases to full strength: when, on the contrary, the angle
between two of these faces comes round, the observer is in darkness.
By these alternate changes, the characteristic of the lighthouse is as
distinctly marked to the eye of the mariner as the opposite extremes
of light and darkness can make it. The _flashing_ light is a
modification of the revolving light, and is practically a beautiful
example of the infinite celerity of the passage of light. The
reflectors are here also ranged upon a frame, with faces which are
made to revolve with considerable rapidity; and the light thus
emerging from a partial state of darkness exhibits a momentary flash,
resembling a star of the first magnitude, and thereby produces a very
striking effect. The _intermittent_ light bursts suddenly into view,
like a star of the first magnitude, and continues a stationary light a
minute and a half, when it is as suddenly eclipsed for half a minute;
and by this simple arrangement a strongly marked distinction in the
lights of the coast is introduced. This is accomplished by the
perpendicular motion of shades before the lights. A variety of all
these lights is introduced by interposing before the reflectors plates
of red glass, which produce the beautiful red light alluded to in the
lines of Sir Walter Scott, when he notices the 'ruddy gem of changeful
light.' The red and white light is caused by the revolution of a frame
on the sides of which the lights are placed alternately, with and
without coloured media. There are varieties in this kind of light,
some being so arranged that two white lights shou