The midland journal. (Rising Sun, Md.) 1885-1947, 1891-06-26

Polarized Light.
"There is not the least doubt in my
mind that the problem of photographing
in colors will be solved before long, said
the eminent expert, Mr.. Smillie, of the
Smithsonian Institution at Washington.
II anticipate that within the next 10
years this long sought object will be at
tained. Atpresent the most distinguished
experimenters in photography all over
the world are engaged upon the subject,
and already they have arrived at par
TALLY successful results. There is one
Frenchman who claims that he has
actually discovered successful process,
though others dispute his assertion.
"You must understand that photo
graphing in colors is, in one sense, no
new thing. As early as the days of the
daguerreotype it was sometimes accom-
plished by accident. That is to say, once
in while the sun picture would be found
to have reproduced a color in some
mysterious way that no one knew how
to explain. It has since been surmised
that the curious result was due to a
trace of copper that got into the sensitive
surface. AT all events, copper has been
used in efforts to get colors since, and with
some degree of success. However, it has
been found much better for the purpose
to use chloride of silver, which is made,
by exposure to light for certain time,
sensitive to color waves. But the trouble
has been with experiments in this line
that the colors would not remain. They
can be produced usually now, but how
to fix them is the difficulty, so that they
will stay. Nevertheless, before very long
the secret will be such no longer, I ex-
pect, and portraits and other pictures will
be painted in colors by the camera.
"A great improvement has recently
been introduced in the shape of sisochro-
matte plates, made with new chemical
composition, which, though they do not
reproduce the colors actually, do give, in
a way that they have never hitherto
been given, the values of the colors of
objects. To explain what 1 mean, look
at those two photographs of vase full
OF flowers. The vase was in light yellow
and the bouquet was made up of yellow
jonquils, blue hyacinths, and white
narcissus. One of the photographs is
from an ordinary plate, and you will OBJ
serve that all the color values are lost.
The narcissus comes out white, because
it is white; but the yellow vase is made
black, forthe reason that yellow takes that
way; the jonquils are nearly black also,
and the hyacinths look anything but
blue. Now, on the other hand, look at
this other photograph, which is of the
same vase and posy from an 'isochro-
matte plate. You see that in the latter,
though no colors are produced, the tints
are so well given by the shading that the
hyacinths really look blue and the
jonquils and the vase light yellow as in
the original. This you can not help ad-
mitting is in itself great step ahead.
@Color photography would be great
help to us in our work of making photo
of sections of rocks. In the
SO called astrological division of the
National Museum we try to exhibit the
various rocks Of the world in four ways.
We show, first, block of a particular
kind of stone. Next, we give in figures
the supporting strength of that stone.
Third, we offer picture in water colors,
showing how building made of that
stone will look. And finally we hang up
on the window, where the light shines
through it, greatly magnified section
Of the stone as it is seen under a micro
scope by polarized light. For this last
purpose small piece of rock is ground
down until it is the thinnest possible
film. A ray of light is passed |
through prism of Iceland spar, which |
has the peculiar property of so separat-
ing the light waves as to 'polarize' the
light, as the technical phrase is. Pre-
cisely the meaning of this it would take |
too long to explain in detail, but it is suf-
ficient to say that it has certain effect |
Of refraction which accomplishes the pur-
pose wish to describe.
"The ray of light, having gone through
The prism of Iceland spar, passes ON
through the film Of rock, which is
on a glass plate, and beyond
which is fitted into camera. Thus a
very much magnified image of the rock
ection is thrown upon the sensitive
plate inside the camera and big picture
If it is made. The picture is merely in
black and white. but the image produced
IN the ground glass at the back of the
'amera is in all sorts Of beautiful colors,
'ach element of which the stone is COM
,osed being made by the refracting effect
# the polarized light to take on tint of
is own, so that the least pretty bit of
ordinary cobblestone is a patchwork of
ovely hues. AS it is we are obliged TO
int the photographs with water colors,
opied after the image on the ground
lass; but, if we had way to photo
raph colors, the exquisitely tinted pict-
Ires of the stones could be obtained
lirectly.
"f you care to look at the windows in
he south wing of the museum, which
ight the Theological exhibition, you will
ee number of these colored photomi-
rographs just as they would appear to
our eye if you looked at the originals
through microscope. They are put up
n the windows in order that the light
nay shine through them and show their
exactly as would be the
ase if you were employing microscope
or the examination of the sections.