chools of New York and
Brooklyn, during the past year, set an example which some of our
millowners might profitably follow. There have been cases when, from a
sudden alarm of fire, children have been crushed in their crowding to
get out of the building. The teachers, in the instances referred to,
marched their children out, under discipline, as if there had been a
fire. Let owners of factories try some such plan as this, by which
workmen may be called upon to cope with an imaginary fire, and many of
them will, we venture to say, find means of improving their present
system or appliances for protection, elaborate as they may at present
think them to be.

* * * * *

WHAT IS LIGHT?

If on opening a text book on geology one should find stated the view
concerning the creation and age of the earth that was held a hundred
years ago, and this view gravely put forward as a possible or
alternative hypothesis with the current one deducible from the nebula
theory, one would be excused for smiling while he turned to the title
page to see who in the name of geology should write such stuff.
Nevertheless this is precisely similar to what one will find in most
treatises on physics for schools and colleges if he turns to the subject
of light. For instance, I quote from a book edited by an eminent man of
science in England, the book bearing the date 1873.

"There are two theories of light; one the _emissive_ theory; ... the
other, the _vibratory_ theory;" just as if the emissive or corpuscular
theory was not mathematically untenable sixty years ago, and
experimentally demonstrated to be false more than forty years ago.
Unless one were treating of the history of the science of optics there
is no reason why the latter theory should be mentioned any more than the
old theory of the formation of the earth. It is not to be presumed that
any one whose opinion is worth the asking still thinks it possible that
the old view may be the true one because the evidence is demonstrable
against it, yet while the undulatory theory prevails there are not a few
persons well instructed otherwise who still write and speak as though
light has some sort of independent existence as distinguished from
so-called radiant heat; in other words, that the heat and light we
receive from the sun are specifically different.

A brief survey of our present knowledge of this form of energy will
help to show how far wrong the common