finger-tips of static electricity accumulated by shuffling the feet
across the floor-rug.

Although many of these methods and devices have been used primarily for
making fire, they have served as emergency or momentary light-sources.
In the outskirts of civilization some of them are employed at the
present time and various modern light-sources require a method of
ignition.




III

PRIMITIVE LIGHT-SOURCES


Many are familiar with the light of the firefly or of its larvæ, the
glow-worm, but few persons realize that a vast number of insects and
lower organisms are endowed with the superhuman ability of producing
light by physiological processes. Apparently the chief function of these
lighting-plants within the living bodies is not to provide light in the
sense that the human being uses it predominantly. That is, these
wonderful light-sources seem to be utilized more for signaling, for
luring prey, and for protection than for strictly illuminating-purposes.
Much study has been given to the production of light by animals, because
the secrets will be extremely valuable to mankind. As one floats over
tide-water on a balmy evening after dark and watches the pulsating spots
of phosphorescent light emitted by the lowly jellyfishes, his
imaginative mood formulates the question, "Why are these lowly organisms