Year: 1863

Orange,


Red.


Now If we examine this spectrum very care
fully we shall notice crossing it, many dark
lines which differ much in width and distinct
ness. These lines have been carefully studied
by Fraunhofer, and are collectively called by
his name. He noticed that these lines always
maintained fixed relation to each other, when
the ray of light emanated from any given
source, but this relation varied when the light
was changed. Thus sunlight, coming through
any prism, had its defined lines which never
changed their relation. If the ray came from
a candle or from a calcium light, the dark lines
were different from those produced by sun
beam, but still these had always the same re-
lation to each other no matter what kind of
prism was used.


The two chemical philosophers, whose
names head this article, found that not ouy
were the foregoing facts true, but that much
more could be gained from pursuing the same
line of experiment. They discovered that a
ray of light coming from burning Potassium
had a spectrum of its own, and that one OF So
dium or Lithium had one equally distinct.
They, moreover, saw that by telescope could
be observed certain bright lines in each spec
trum peculiar to each metal upon which they
experimental.


The instrument, contrived by them to see
the spectra of burning metals, is easily under
stood by means of a diagram, but this, unfor-
tunately, is denied me. | shall ask the reader
to imagine a small box in which are inserted
two tubes at an oblique angle. One of these
tubes Is telescope cylinder, and is direct
ed toward prism of Bisulphide of Carbon lin
glass;. The other tube coming from a differ
ent direction also looks toward the prism. In
front of the latter tube is gas jet in which
burn coal gas and air commingled. The light
of the flame is almost invisible, but the heat is
intense.


The lamp is lighted. and we are ready. Look
through the telescope, and you see only
gmmer of faint light.


Now, while you are looking at the prison,
let me place piece of Potassium in the Jet of
gas.


You now see a spectrum in which are dark
lines and bright lines and lines of many colors.
Replacing the Potassium, by another aka
line metal, Sodium. you will observe a differ
ent spectrum. The lines are changed.


And so on, through the whole list of the
elements. For each one which can be burn
ed IN the gas jet or In the electric heat, you
will see different and peculiar set of lines.
Moreover the spectra do not change the re-
lation of their lines. The Sodium spectrum
is always constant and its lines are the same


Now as these experimenters were studying
the spectra with diligence they happened to
examine the residue of mineral water from a
spring in Germany. They saw, as they burned
the residual particles in the jet, new spec
trum In which was distinct and peculiar blue
band. They were unable to refer it to any of
the known elements, and SO considered it a
new one.


Not satisfied with these trials, the chemists
evaporated twenty tons of the same mineral
water. From the residue, they were able to
form "a platinun-sali' of the new metal.


Thus found, they must give it new and ap-
propriate name, and they chose


cEsIUM,


which means "greyish-blue," and refers to the
color of the spectral lines. Astonished and