Watertown republican. [volume] (Watertown, Wis.) 1860-1906, 1874-09-30
Wonders of the SpectrOscope.
BY VIM. A. PHELPS. A, M.

IF through a small circular opening
in the shutter of darkened room
ray of sunshine be permitted to pass,
there will appear round white spot of
light, an image of the sun, on the oppo-
site wall OF on q screen occupying the
intervening space.
But, if a triangular prism of cut
glass be so placed as to intercept the
tiny ray, and allow it to pass through,
brilliant spectacle presents itself on the
screen. On it's emergence from the
prism it no longer remains single ray
Of white light as it passed through the
opening, but is dispersed into several
colored rays, which, as they continue to
d1verge, form upon the screen an elon-
gated band of beautiful hues instead of
the sun-image, as first described. In
this gorgeous band each particular color
blends gradually into the others, begin
ming with the red. The dark red ray
passes imperceptibly into the orange,
and the orange again into bright vel
low a pure green succeeds, and is
shaded off into a brilliant blue, which
IN turn gives place to rich, deep indigo,
while a delicate purple leads finally to a
soft violet, and thus the range of the
visible rays produced by the decompo-
sitiOn Of d sunbeam is terminated This
magnificent picture of dispersed solar
ray IS called spectrum; and the exper-
iment which we have described proves
beyond question that white light is de-
composible. And hence the prism may
be said to analyze light which is made
If hn w oo1 81,
referred to. This grand discovery of
the composite nature Of light was made
by Sir Isaac Newton in 1874. If now
the spectrum be examined with the aid
OF small telescope, it will be found
that this band of colOrs is not cOntinu-
Gus, but that it is interrupted by hume
rous dark lines running across it. This
discovery was made by DR.. Wollaston in
1902, and again by Frarnhofer, a Ger
man optician, in 1915. By great i'm
provements lii the optical instruments
employed, Fraunhofer discovered the
relative distances of these lines from each
other, and that for sunlight these dis
tances were always the same. He also Sue
ceeded in mapping no less than fifty
lines as belonging to the solar spectrum.
Hence they are called Fraunhofer's
lines. Since his day, however, addi-
tional discoveries have revealed the fact
that there are thousands of these lines,
thus breaking the continuity Of this
wonderful sun-picture It has like
wise been ascertained that the lines ex-
ist IN reflected as we'll as direct solar
lights. They maintain the same posi-
ton in planet-light as in sunlight
Fraunhofer also made the important
discovery that in the spectra of the fixed
stars there were dark lines differing
from those formed in the spectrum of
the solar ray. Hence the conclusion
was reached that the origin of these lines
must be found in the source Of light it
self
Physicists were thus led to examine
the spectra of artificial light. Tt had
long been known that certain chemical
substances, especially the salts of aka
lies and alkaline earths, when strongly
heated in a blowpipe or other nearly
cOlorless fame, impart to that flame a
peculiar color by the occurrence of
which the presence of the substance
may be detected. For instance, the So
dunn compounds color the fame an in
tense yellow, whilst the potassium salts
tinge it with violet. The yellow soda
color is, however, SO much more intense
than the purple potash tint, that very
small trace Of soda prevents the eye
from detecting the purple, seen if large
quantities of potash salts be present
But by the aid Of the prism this diff
Guilty vanishes, and the presence Of
many different substances in the flame
may be with certainty determined by
the color of the lines which their spec
TIA yield. In this way different chemic-
al elements, such as iron, sodium, potas-
SUM and hydrogen were subjected to a
white heat, and the light thus
emitted by each was passed through
prism and their spectra were
observed. Through these experiments
it was discovered that in place of some
Of the dark lines Of the solar spectrum,
bright lines of different colors according
to the substance experimental upon,
appeared. Thus the metal sodium
yielded a spectrum containing bright
yellow line, corresponding in position
with a certain dark line in the solar
spectrum; potassium gave two bright
lines, one corresponding with certain
dark line at the red, and another with
similar line at the violet end of the
spectrum. Further experiments have
proved that the spectrum of each chem
ical element yields one Or more bright
lines, as the case may be, of particu-
lar color, corresponding in position
with the dark lines of the spectrum of
sunlight and these peculiar lines are
always produced by the same chemical
element and by no other known sub
stance, while their position is never
changed.
It may be further stated that recent
investigations have established the fact
that there are three classes or orders of
spectra, depending upon the condition
and circumstances OF the source from
which the light emanates. These orders
are:
1. Incandescent, or white hot solid
and liquid bodies give continuous
spectrum, that is, one not interrupted by
any lines whatever.