Year: 1873

I'm the above diagram, which furnishes comparison
Of the bright lines in the spootra Of terrestrial sub
stances with the dark lines IA the solar spectrum, the
band ION the left represents the solar spectrum the
spectrum OF sodium g. that Of thalium A. of silver; 8,
OF nthium.l


HOW KIRCHoFF REACHED HIS DISCOVERIES


Now, Kirohhof had made thoroughly clear to his
mind the principles which linked together the
emission OF light and the absorption OF light; he
had proved their inseparability for each particular
kind OF light and heat He had proved for every
specific ray Of the spectrum, the doctrine that the
body emitting a ray absorbed with special energy q
ray OF the same refrangbty Consider then the effect
ofknowcdce such as YOU now possess upon mind pre-.
prepared ike that of Kmchho We have seen the mean
descent vapors OF metals emitting definite groups OK
rays according 10 KIrchhOhs principle those Vapors


crossed hy solar hight ought 10 absorb rays OF the same
Tcfrangblity those which they emit lie proved this
10 he Tire case he was able by the nerposton vapor
TO cut ont Of the spectrum, the band correspond
ing color that vapOr Now the sun possesses phOto
sphere or vaporous envelopes doubtless mixed with
violently agitated clouds and Kirchhon saw
that The powerful rays coming nom tho s0lld
bv This vapor One dark band Of Fraunhofer FOR ex-
ample. occurs in the yellow Of the spectrum. sodium
band hersc KrcAho inferred the existence OF sodium
vaVur Ia tbe atmosphere OF the sun. In the case Of
metals which emit large number OF bands, the aDso-
luto cocdcuce OF every bright band of the metal with
dark Frauuhoer hue raises to the highest degree OF
certainty the inference that the metal is present
IN the atmosphere of the In this way solar
chemist, wac founded on spectrum analysis


EMISSION AND ABSORPTION ISTERPRETED.





analogy sound the ply steal meaning of emission and
absorption draw a iddle-bOw across this tuningfork
and it Immediately fills the with musical sound
this is The radiation emission OF sound from the fork
few days ago. sounding this fork, noticed that
when s vibrations quenchod, the sound seemed 10
be continued. though more feeby the sound appeared
20 come under the table where stood number 0i
tuning forks OF different sizes and rates OF vibration
one oi these, and only had been started by the
fork. and IL was whose rate Of vibration was the
same that OF the fork which started IT, This is an IN
SfQ Oft q
other Placing two forks thus each other sweep
ing the bow over of them and then
ouenchinc The agitated fork the other continues
20 sound Placing a cent piece on each prong OF one
OF the forks destroy its perfect synchfOnlsm with
the other, and then no communication or sound
from tlr the other is possible will now do with
light what has been here done with sound. Placing
tin spoon containing sodium in Bnnson's flame we
obtain tls intensely yellow light which corresponds IN
refranglility with the yellow band OF the spectrum.
will send the white light from our lamp through that
flame aud prove LefOrc YOU that the yellow flame inter
cepts yellow the spectrum, producing 10 all ntents
and purposes dark FTaunhOfers band IN the place OF
the yellow.


FEyFEsAL OF THE SODIUM BAND