The morning call., 1894-05-13

figured. The other parts Of the instrument
are solely for the purpose of sending the
light properly through the prism and re-
ceiving it after emerging from the prism.
The light coming 10 us from the sun. or
star, or a comet is very complex, and the
effect of the prism Is to sort ouI all the dill
ferent kinds OF light and arrange thecl
side by side. This aIran gemen. Oh the 2
light of body is called the spectrum OF
that body The observer records Its form
and arrangement, either by visual observa-
tions, or upon a Photographic plate. CON-
pares it with the spectra OF our we'll
known chemical elements, and draws MS
conclusions.
In the case of the present comet the
spectroscope was directed upon that part
of the object inclosed in the dotted lines
(see fig. D. The light coming to US from
the very narrow central strip OF the comet
entered one end of the spectr0scope. The
prism sorted out the different kinds of light
and arranged them as shown ln the upper
half of the drawing Zig. 2) The spectrum
of the comet was observed to consist Of
yellow band Uhe one furtnest to the LETT,
a green band, blue band and twenty five
bright lines. The positions of the bright
lines were measured as accurately as pos
sible: those In the yellow and green by
visual methods. and those in the blue and
violet by Photographic methods.
After the observations we're completed
il remained to interpret them. The comet
srectrum is unlike that of the stars, the
nebulR and Otner celestial objects. The
spectra of our chemical elements differ
widely from each other. The spectrum of
iron, for instance, is characteristic oil iron
and will never be confused with that of
lead or tin or other elements. Ihe ex-
perienced spectroscopic observer will very
quickly identify the chemical elements by
af hal
burned at a very high temperature it will
yield the spectrum of three bands and ten
superposed bright lines, as shown IN the
left end of the lower half of figure 2. Ii
cyanogen, which is composed OF
carbon and nitrogen combined, be
burned at high temperature 1t
will yield the spectrum OF eight
bright lines shown in the right end of the
lower half If fig. Q. Now. glance Is
sufficient to show inat the carbon spec
trum is matched perfectly by the lett
half of the comet spectrum, and that
the light cvanogen carbon and nitrogen)
lines are matched perfectly by light comet
lines. A few Of the comet lines, seven ln
all, do not have correspo ponding cyanogen
lines. The origin of the seven lines re-
mains in doubt. They may be due to
chemical elements other than carbon and
nitrogen, or, more probably, to conditions
| of heat ana pressure which we cannot
match in laboratories.
There can be no doubt OF the fact that
the comet is composed almost wholly oil
carbon and nitrogen.
| It has been known for twenty-five years
tina carbon exists prominently in comets,
| from observations by DR.. Huggins and
Others. Sodium has been found in one oil
two comets. 1t was not until July, 1898
| from Lick Observatory photographs oil
! the spectrum of the bright comet then
visible, that the prominence Of nitrogen in
Comets was established.
The spectrum of the interesting Holmes
comet of November, 1892, was of an en-
tirely different character. 1t did no