yed?"

"They pointed out that at certain stages of the world's history great
floods came and destroyed all the people inhabiting the low places, and
at other times the terrific volcanic eruptions destroyed those who lived
in the hills, and at other times entire continents, like Atlantis,
disappeared, so that the earth had to be repeopled and the arts and
sciences learned over anew."

It is wonderful to relate how the life on the island affected the health
of all. They lived outdoors and had plenty of sunshine and vigorous
exercise. In the laboratory, the Professor made it a constant habit to
do all his work in the sunlight, to which he exposed himself at all
times. The boys often spoke of this, and one day, while talking on the
subject, he remarked:

"It is surprising how little the majority of people value sunlight. It
is not the visible sunlight that performs the wonders in giving strength
to man. If you recall, we spoke about the actinic rays which cause the
chemical changes on the photographic plate. It is those unseen rays
which produce the aurora borealis, exert a curative effect upon leprosy
and tuberculosis, fill the atmosphere on the sunny side of a street with
oxygen and nitrogen, and do many other marvelous things."

"In what manner does the invisible light produce these results?"

"In its sparkling radiations microbes die, decay ceases, the iron in the
blood becomes chemically strong; ozone is manufactured from the dirt and
dust, which are also destroyed; the perspiration becomes active and
carries off waste from the muscles and cleanses the skin; dead tissues
are purified and the muscles invigorated; and all life is made to
thrive."

"Does the sunlight have the same effect on all the animal creations?"

"This is true of all animate life, except minute organisms, or what are
called bacteria."

"If that is the case, why do worms and the like hide themselves in the
earth?"

"In that case it is the instinct of self-preservation. The most of them
are eyeless, so that sunlight exposes them to birds and other enemies.
Professor Mast demonstrated that they are very favorably influenced by
exposure to sunlight. Dr. Dolly has shown, by a series of very brilliant
experiments, that the butterfly will live three times longer in sunlight
than in the shadow; and Professor Yerkes has also proven that the
jellyfish, while inactive in the dark, becomes very strenuous in
sunlight."

"If that is the case, why woul