Year: 1873

lin the diagram, is substance raised TO luminous
temperature by means Of the flame OF spirit lamp 2
ss prism which the luminous are conveyed
and by which they are detected the at A can
die at d used illuminate scale for purposes OF
sDeaurement an image of which is also carried TO the
eyeatA.J


The hight passes from the spectroscOpe through mar
row aperture which is termed slit then falls upon the
PRISM and wher falls upon the prism undergoes re-
fraction being bent out course aud also undergoes
dispersion being resolved into its constituents; and
then by little telescope this dispersed light
the image similar TO that which produced on
The screen which the spectrum This instrument is
The form uf apparatus which you see here, and the
various parts OF which have named are all present.
These three parts essential to The specrOscope, and
when these exist the spectroscope is complete, We
have for example in this end Of the spectroscope mar
row opening between the pieces OF metal This opening
IL called Slit The line OF light which passes


between these pieces metal then falls upon this lens
and is rendered parallel This is prism OF flint glass in
which II is bent and 10y which it is dispersed, until


finally il passes this telescope TO which the eye is
p.aeod and views the spectrum produced Beside this
IL frequently convenient 10 indicate the position OF
lines aud there is here third telescope, by means OF
which the image Of the scale which is photographed is
placed in this end and illuminated by the lamp placed
near IT, scale thrown through the telescope, and
reflected surface Of this prism through the
telescope.





somprehensive term. When say that when light passes
through the prism obtain spectrum, make gen.
eral and not a specific statement For light may he OF
various and kinds. We may have white light; for
instance light OF the the stars and the ordinary


eliminating agents. White light, however. is the
parative term all light We call white all Light which
comes 10 us from the celestial bodies yet is how
ever a strong yellow star. We know on the other
hand various lights which not white; az the displays
of pyroechuy with It's coored lights and eolored fires
Now obvious that this experiment OF the colored
hghts ought 10 give different spectra from the white
and tba, white lights have very different nature and
character connection with the spectra which differ
from eac other, simply the word light upon the
general principle that white light gives spectrum
which consists OF all cOOTs; beginning with the color
that the least bent the red and passing through the
seven colors ordinarily called the rainbow colors We
pass from red 10 orange yellow to green blue, indigo
violet not only these seven colors, but through
every intermediate shade between them.


We have IN the white light continuous spectrum con-
tanning only these seven coors but every inter-
mediate shade of the eOlors On the other hand, in
the spectrum Of the coOred light have only part Of
tbe eoOrs present; and that is perhaps natural, we
reject upon the fact that the why the
hight Is ooored s that part Of the color TO make the
White u wanting For instance, take out the red, the
bloc OF the yellow from the white and the rest Of the
ooIors combined will not make white but some other
color and the hight which results OF will be col
0red. IL important for for moment 10 consider
fhe Of the light which is produced when heat


body. Take, for instance piece OF iron; put 1t In
the FIRE and gradually raise the temperature until the
iron becomes luminous and you the red color; and
the temperature rising. you the yellow and finally
oomes the white heat Examine IL the spectroseope,
and the first color red truly; the second,
the red is st there, proporonatey and as the heat
continues the red exists the less the spectrum
takes the successive cOors, until finally full white is
developed. We say the iron Is At white heat On the
other hand, IL we take gas we find as soon as II
bocOIDes at all II gives light OF certain color
which ie maintained through the whole. Take oxygen


as yben 10 luminous look at the through


spectTOsoOpe and you perceive totally different spec
that OF ron raise the temperature no matter
much and the spectrum remains the same. Herein


gas different from sOhd ~ 10 IT'S spectrum IL Is
which the solid Is true OF quid; hut that
winch is true OF a is also OF vapoT. What II the
reason of this dsnctiODf Physcsts Tell ns that IL 10
The molecular vibration Of the constituents which
set in notion the vibration OF the molecules Of
SOLIDS in the bTe, which we call hght, ls exceedingly
COMPLEX while the motion Of the molecules OF gases IL
of the molecules OF gases, communicating MOTION To
eher call light while IN the case OF sOlus ana
llauide this cannot be done


W. fnd therefore in the heat of gases that the vbra
lion IA maiptsined No matter what the temperature
velocity Of motion 10 be- increased, the wave
ugtbs remain the same; while IN the case Of solids the
lengths successfully have all measures 10 that we
have a continuous iDcandescent spectrum Thus we
eaD tell bV examining the spectrum OF body wbethtr
fhe light which examining comes from s0Dd "
bquld or from gas II throw the light IN the spec
troseope, and The sptcsroscops gves
so1d or liquid; IL IL gives ns an interrupted spectrum
a. ese than all the present. then we kDow that
ths source OF light IL easeous M fTanEiaoa M @ nas
rare tsfy give eeDeseees epteffA Lbs newaltcs W ]