National Republican. (Washington City (D.C.)) 1872-1888, 1875-01-06

Every child, however. knohs tnat Olue III ~
yellow paints, when mingled, make green. why
" With With the aid of the diagram Fig. 81 will ex;
that paints show color by transmitting light
through them to and from the paper on Hnien
they are used. blue paint is one when tTans
yellow paint transmits only red, yellow, orange
and green. Thus, white light, which has been
Obliged to filter through such blue and yellow
pair Of particles will have nothing but green left
II however, we throw the light transmitted
mitted by the blue paint, we will evidently have
all the colors represented and therefore an lm-
preston Of white produced.
To illustrate this further, will now take the
pieces of eoored glass Just used to obtain the blue
and yellow lights, which, united, made white, and
will place them over each order in the same
lantern so that they will act as q double filter,
such as we have described; you then see that
they produce bright green color.
yellow paint is mere accident OF the expert
mept, and the primary cOlors OF 4ouns-red,
green and VIolet-are the true simple Impressions
and net those Of Brewster-red, yellow and blue
FATIGUE OF THE EYE.
There il, however, another property OF the eye
as regards its perceptions Of color which must
not be forgotten. ~
fatigue, and with fatigue comes diminutton OF
power or constituencies and this not only in gen.
eral way, but as regards its Individual capacL
thus, suppose the eye to be exposed to red
light, the perception Of red is soon fstigued and
dulled and If then white light be viewed, the red
due Impression and the white light will seem col
ored by an excess of the other tints.
made TO seem Of any tint BY contrasting it in this
way with some strong general color. Thus; l
have here two lanterns throwing towards the
object, B, is placed as to throw on the screen
two shadows. At r., it is clear, the white light
does not tsll hut only the red, ana az W" vas az
which Of you for moment would suppose that
this was white and not blue green? If make
6s E5fSs ut e tSsn did BE-
fore when 1t was actually white Now remove
the red light and substitute green, and then you
see the white part looks red as it before looked
green, and so we can change 1t at will.
EFFEcr OF CONTRASTS IN COLOR.
This principle, as involved in what is called the
effect Of contrast, is Invaluable to the painter
BY iudicious use OF brilliant contrast color be
and thus develops some OF the loVeliest result Of
| his ar.
| one lantern o picture of q statue, with back
| ground OF foliage, From another lantern throw
over this an even disk OF light, and on this plate
an opaque silhouette corresponding in outline with
| the statue. BY this means the statue is shaded
| from the light coming from the second lantern
which falls, however, on all other parts Of the
In the second lantern, paint at stroke all but the
/ statue with tinted light. now introduce red
| Elaeg, and you see tnat the IOllage looks
the statue Is no longer white but green, and now
| with green glass, We make the foliage green
and the statue, whose color has IN fact never beer
as il we're, paint an object without color, make
red by using green, and ufes versa.
THE PowERs AND DEPICTS OF THE EYE.
| In speaking Of the eye in its relation to color
and Of its power Of discriminating between differ
ent wave lengths, have used expressions i'm
| plying imperfection and error in It's action; nnd
| lest should convey an impression which would
be as far from my intention It is from the fact
Of the case, must say few words in explana
ton.
Discrimination between wave lengths is mol
only not the true Office Of the eye, but would b
quite inconsistent with its varied and indlspenss
| bic functions as an organ OF vision.
THE EVE AS sPEcTRoscoPE.
II is perfectly true that the eye, as q spectre
scope, Is a miser8b BILE instrument; but who, wher
gazing at the glories Of q crimson sunset, 81 thu
beauties Of q yariegated Landscape, or the blend
ed roses and lilies OF pretty face, would chang
his eyes for pair Of the finest spectroscopes tina
have ever left the shop Of the most skillful Opt
| clan!
II is common and natural, in comparing the eyl
to this or that special instrument, 70 alude to IL
differences in terms implying defect. But Till
does not, and should not,carry With 1t any idea
reproach.
THE Eye AS AN ORGAN OF VISION.
In speaking of the eye as an optical instrumen
one Of our ablest physicists, HelmholtI, has uset
Q form Of expression, which, quoted alone ant
without reference to the general spirit OF the con
| text, would convey the impression that the cyl
was held in contempt as buAgling piece Of work
manship, unworthy Of any skIllfUI optieian.
Any candid reader who peruses the entire pas pas
the mesning Of the author as It e from the fact
Indeed. Helmholtz's Investigations themselves
show that. wherever inii knoHledge has oe si
better method in an optical instrument is an 10
stance Of the admirable adaptation Of the eye Il
its larger and more complex functions as an organ