without light; that a slight
discoloration only will be produced by the red rays; that the effect of
blackening will be greater towards the violet end of the spectrum; and
that in a space beyond the violet, where there is no sensible heat or
light, the chemical effect will be very distinct. There seem to be rays,
therefore, more refrangible than the rays producing light and heat.

The general facts of the refraction and effects of the solar beam offer
an analogy to the agencies of electricity.

In general, in Nature the effects of the solar rays are very compounded.
Healthy vegetation depends upon the presence of the solar beams or of
light, and while the heat gives fluidity and mobility to the vegetable
juices, chemical effects are likewise occasioned, oxygen is separated
from them, and inflammable compounds are formed. Plants deprived of
light become white and contain an excess of saccharine and aqueous
particles; and flowers owe the variety of their hues to the influence of
the solar beams. Even animals require the presence of the rays of the
sun, and their colours seem to depend upon the chemical influence of
these rays.

Two hypotheses have been invented to account for the principal
operations of radiant matter. In the first it is supposed that the
universe contains a highly rare elastic substance, which, when put into
a state of undulation, produces those effects on our organs of sight
which constitute the sensations of vision and other phenomena caused by
solar and terrestrial rays. In the second it is conceived that particles
are emitted from luminous or heat-making bodies with great velocity, and
that they produce their effects by communicating their motions to
substances, or by entering into them and changing their composition.

Newton has attempted to explain the different refrangibility of the rays
of light by supposing them composed of particles differing in size. The
same great man has put the query whether light and common matter are not
convertible into each other; and, adopting the idea that the phenomena
of sensible heat depend upon vibrations of the particles of bodies,
supposes that a certain intensity of vibrations may send off particles
into free space, and that particles in rapid motion in right lines, in
losing their own motion, may communicate a vibratory motion to the
particles of terrestrial bodies.

MICHAEL FARADAY

Experimental Researches in Electricity

Michael Faraday w