s possible, and that is color blindness. The boy who is
a color blind will always remain a color blind, and as forty in every
1,000 of the male sex are color blind, it is essential that they know
their defect, and train their course accordingly. It would be to the
advantage of all boys to undergo such an examination once in their
school life; a color blind would be useless where the selection of
color entered into his life work. If a boy had a talent for drawing or
engraving, and were color blind, he would make a success of his life,
whereas if he would attempt to mix paints of different colors he would
be a failure.

I shall not dwell upon the scientific part of color blindness, nor
discuss either the Young-Helmholtz or the Hering theories of color
defect, but shall deal with its practical use in everyday life.

Until the year 1853, very little was known about color blindness, and
much less written about it.

Dr. George Wilson, in 1853, wrote several articles, which were
published in the _Edinburgh Monthly Journal of Medical Science._ These
articles created such an interest in the scientific world that Dr.
Wilson brought out a book, entitled "Researches on Color Blindness,"
two years later. So thoroughly did Dr. Wilson sift this subject that
no writer up to the present day has added anything practical to what
was then known.

Dr. Wilson writes in his preface: "The most practical relation of
color blindness is that which it has to railway and ship signals." He
further states: "The professions for which color blindness most
seriously disqualifies are those of the sailor and railway servant,
who have daily to peril human life and property on the indication
which a colored flag or a lamp seems to give."

Dr. Bickerton, in an article on this same subject, speaking of the
careless way in which lights were used on ships at sea, says: "Until
the year 1852, there were no definite rules regarding the carrying of
lights at night by vessels at sea.... At this time the subject of
color blindness had not awakened the attention of practical observers,
and had the fact been known that between three and four per cent. of
the whole male population are color blind, some other mode might have
been devised to indicate the positions of vessels at night than by
showing red and green lights."

If it is so very important to have sailors with good color perception,
where, at least, four men are on the lookout, how much more important
is