them as vellow. Red and green, then, are
the two colours which the colour-blind are
least able to appreciate. It is one of the
most ordinary cases in connection with colour-
blindness, that A or B, seeing a scarlet
verbena in full blossom, can detect, at a little
distance, no difference in colour between
leaves and flowers, or can perceive no
contrast of colour in ripe cherries and the foliage
of the cherry-tree. Yet it so happens that red
and green are the two colours commonly
employed in railway and ship signalling!
Of course there is no folly or ignorance
imputable to anybody in the matter. The colours
contrast vividly to ordinary eyes, and when
the signals were established little was known
of colour-blindness, nothing of the extraordinary
frequency of its occurrence. It simply
happens to be an odd coincidence, that,
considering the matter from this point of view,
precisely the wrong colours have been chosen.
One great railway company, having been
made acquainted with the nature and extent
of colour-blindness, has already felt it to be
necessary to admit no person to the post of
guard or signal-man until his sense of colour
has been tested by a regular examination.
The difficulty may be tolerably well overcome
by the use of this precaution, but, as we shall
presently point out, in adopting Dr. George
Wilson's suggestions, there may possibly be
better ways of overcoming it.

We will first draw upon Dr. Wilson's
experience for a few illustrations of the subject.
In one of his cases, a gentleman (Mr. A.)
studying medicine at Edinburgh, was baulked
in his love of chemistry by an inability to
decide upon the colour of precipitates, and
among other points mentioned by this gentleman
was the following. Before studying
medicine he had, for some years, followed the
profession of a civil engineer. When acting
as assistant to the engineer of the Granton
railway he frequently returned in the evening
from Granton to Edinburgh on one of the
engines, taking no part in its management.
On these occasions he observed that, although
his undivided attention was directed towards
the signal lamps, the light of which was visible
to him a long way off, he could not, till he
was close upon them, distinguish whether
they were red or green. He felt certain that
he could have distinguished between a blue
and a red light at a distance which made red
and green appear the same.

Another gentleman, Mr. B., sees in the
rainbow no colours but blue and yellow; red
on the lips and cheeks appears as blue to
him; and yet, when once asked to represent
with colour from a paint-box his notion of
the colour of the lips, he chose an earthy
green to do it with. This gentleman, when
requested to collect together all the greens
that he found in a heap of variously-coloured
glass, put, side by side, green, red, brown,
yellow, claret, and pink; when further asked
to state which green appeared to him the
rarest, he at once chose the claret-coloured
glass.

In this case, as in most others, it was to be
observed that a great part of the difficulty
disappeared if the colours were observed by
gaslight. Mr. C., who cannot tell a geranium
from a geranium leaf by daytime, delights in
the sight of a conservatory lighted artificially,
because he then appreciates with double force
the contrasts of the colours. There is also
within Dr. Wilson's experience, Mr. D., a
draper, who, being colour-blind, retires from
his shop into a gas-lighted room when he
wishes to perceive the colour of his wares.

Mr. E. says: " I am an engraver; and,
strange as it may appear, my defective vision
is, to a certain extent, a useful and valuable
quality. Thus: an engraver has two negative
colours to deal with i.e., white and black.
Now, when I look at a picture, I see it only
in white and black, or light and shade, or, as
artists term it, the effect. I find, at times,
many of my brother engravers in doubt how
to translate certain colours of pictures which,
to me, are matters of decided certainty and
ease. Thus, to me, it is valuable."

Mr. F., an artist who, in the same way,
considers that his crayon drawing is the better
for his colour-blindness, has, when his crayons
have been displaced, represented trees with
their foliage in red chalks, and put pink crests
to the waves of the sea. When out hunting,
he has been unable to distinguish between
scarlet coats and black ones – a difficulty to
which one or two other colour-blind fox-
hunters have already confessed.

Admiral G. once bought a pair of green
trousers, thinking they were brown, and is of
opinion, as a naval officer, that the colour
alone of flags can never be relied on as
sufficient to distinguish them. " I would
not," he says, dispense with colour, for in
particular lights it assists the eye more than
shape, especially when flags do not blow out,
or are fluttering in the breeze. But, on the
other hand, when transparent bunting, which
has become worn, is seen against the light,
the darker colours are often mistaken for
each other, and therefore it is essential, and
is the practice in the navy, to represent
different colours in different patterns, so that
each tint is connected with a peculiar shape,
and the risk of mistake is lessened."

Professor H. has sketched in sap-green,
believing that it was sepia. Dr. J. never
buys coloured articles except with the help of a
friend, and says, having often observed a railway
signal-light, seen from my window, I am
convinced that its colours would be lost upon
me, nor dare I trust to their flags." Professor
J. writes: " I am sure that I should make a
dangerous railway signal-man, as I most
certainly would not know a red flag from a
green one."

Mr. K., an artist, had a pupil whom he
released from his engagement, on finding
that he copied a brown horse in bluish green,