It is well known that any light created by man wastes a large
percentage of its energy in the production of heat. This is plainly
noticeable even in our electric light, for the bulb soon becomes hot,
when the current is on, and light is produced. Nature is far more
economical. She has learned to produce light which is practically
100 per cent efficient, so that almost no heat is generated in its
production. This is generally known to science as “cold light,” and is
produced by fireflies, glowworms, and certain fish and bacteria, which
create this light for themselves whenever they desire.
A prolonged study of this cold light has lately been undertaken,
with a view to obtaining it artificially; for, if its secret could
be discovered it would have great commercial value, inasmuch as a
large percentage of the energy expended in producing the light could
be saved. Scientists have accordingly undertaken the study of these
light-producing creatures, and much has been discovered concerning them.
In a paper recently read before the Franklin Institute of Philadelphia,
Dr. E. Newton Harvey, Professor of Physiology at Princeton, stated
that the cold light of the firefly is the result of the combination of
oxygen in the air and a substance called “luminiferin.”
This substance is produced by certain glands, specially constructed
by nature for the purpose, known as light-organs. They are virtually
minute lanterns, and are frequently provided with a special lens, which
focuses the light. In the firefly, however, there is no true lens.
The photogenic (light-producing) cells in the firefly contain a mass
of granules, spherical in the male, and short rods in the female.
Each group of cells is surrounded by a clear ectoplasm containing
no granules. Behind this is a layer of special cells which act as
reflectors. Air and water are necessary for the production of this
light.
Much work has been done upon the chemistry of the luminous substances
produced by these living organisms. Two distinct kinds of substances
have been detected. These are known respectively as “luciferase,” and
“luciferin,” which have quite different properties. The former is
unquestionably a protein, and its properties are like those of other
albumins. Luciferin, on the other hand, is more closely associated with
the peptones and proteoses.
This light, produced by living organisms, may have a variety of
uses--such as a warning, to scare away other animals, which would
otherwise feed on the luminous organism; or as a sex signal, to bring
them together for mating purposes; or merely to be used as lanterns.
Many of the deep-sea forms, which live in complete darkness, have no
other light, and it is reasonable to suppose that, in their cases at
least, living light is used for purposes of illumination.
If the secret of this cold light could be discovered, it would probably
save millions of dollars yearly, which is now expended in useless
heat-production; for this could be saved, and a much smaller amount of
energy utilized in the production of light--in which this energy-loss
would not be present.