New-York tribune., 1873-03-03
THE SPECTROSCOPE.
LECTURE BY PROF GEORGE F. BARKER.
Prof. George +. Barker of Yale lectured tC


Prof. George F. Barker of Yale lectured to
very large and attentive audience the Cooper Union
on Saturday evening, on the application OF the
Spectroscope 10 Earth" The lecture, which was the
fourth OF free lectures for the people pro-
fusey illustrated by diagrams and Images on the screen
The lecturer began by referring to the apphoations Oh
the spectroseope to the celestial bodies shown In his
previous lectures reported In full in THE TRIBUNE ana
said that he back to the earth automatically 80
insignificant. The lecturer spoke OF the methods OF
examining substances on the earth by means OF the
spectroscope and placed various substances on the car
bon in his electric lamp as to throw upon the screen
the spectra obtained by their combustion The spectra
shown were complicated ones, having few bright 'but
very many faint lines. The spectra OF tin antimony,
lead iron, znc cadmium, and gold we're exhiolted
The spectra OF zinc and cadmium compared Both
spectra contain three lines In the blue and one In the red
The spectrum OF cadmium in addition contains line In
the green and has the blue lines In different positions
The lecturer then went on to show how the spectre
scope had led to the discovery OF elements before un
known. Prof. Bunsen one day examining
mineral water BY his processes he had obtained crys
tane residue which from the nature Of the processes he
knew 10 be alkaline The only known akalies then were
potassium sodium and lithium. He thought he would
apply his spectroscOpe toward hndng out which one OF
these akalies present He placed htte OF the
substance in flame and watched II through his spectre
scope Instead Of seeing the spectrum of potassium OF
/
two bright blue lines. This spectrum was unlike that
given by tie other akales and showed Bunscn that he
had discovered substance. He afterward evapo-
rated A tons OF mineral water obtained 200 grains OF
the new substance, showed its properties and deter
mined its afinities He gave the metal the name OF
casius blue lines of ts spectrum, the Latin
cGsius signifying blue The Professor described the
processes by which several other elements were dscoy
cred.
He gave an outline OF the Bessemer process OF making
steel illustrating his remarks by diagrams He then
passed to speak of absorption sectra. The absorp
ton specra given by leaf green, blood, oxide OF nitro
gen, and iodine were thrown the screen and eX-
planned. The lecturer then said:
The question be asked, Are not the lines IN the
SUMS spectrum produced by the absorpve action OF our
atmospheric Some OF the lines undoubtedly due TO
this cause. Sir David Brewster showed that the suns
spectrum with the position Of the with refer
ence earth Armstrong and Jansen showed which
lines spectrum due to atmospheric absorption
employed portion Of one OF the large sewers
of Paris, which he filed with steam and through which
light was allowed pass. In this way ii shown
that the aqueous vapOr the earts atmosphere acted
as anel allowing the heat from the sun TO penetrate
the earth, but not allowing 1t to return variety OF
beautiful experiments were then performed exhibiting
the peculiar absorption which various substances such
as cOchinea blood Ogw0Od, and the aDillue colorng
matter magenta exercised on light.
The Professor concluded by thanking his audience Tor
their OF his IabOrs The greater part O tins
lecture has already appeared IN THE TRIBUNE.