Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1919-08-23
Scientific Discussions
by Garrett P. Serviss
By GARRETT P. sERvIss.

BY GARRETT P. SERVISS.
One of the most surprising Of re-
cent astronomical advances is the
accumulation Of evidence that there
are many dark or black, cloudy-look-
ing masses scattered in some places
among and over the stars, which
they partially hide like vast smoke
wells. This evidence is especially
dut to E. E. Barnard, whose exqui-
site celestial photograph and whose
careful and Thoughtful Interpretation
OF the meaning of the strange ap-
pearances presented by them afford
new conceptions Of the universe.
The thought has long been ia
miliar to astronomers that the lu-
minous clouds called nebulae rep
resent an early, and perhaps the
earliest, stage in the development
of stars; in other words. that the
stars are evolved of nebulae some
what as drops Of rain are formed
by the condensation OF water-vapor.
This comparison is intended to go
no further than to suggest vivid
conception of the way in which the
nebulae contract around nuclei, and
by contracting increase in density
until their substance is nearly all
| concentrated into relatively small
spherical bodies, whose temperature
rises to the point of incandescence.
where upon they become stellar
bodies, or suns.
But how the nebulae while yet
in an expanded state are able to
shine, giving off light resembling
j that of incandescent gas, has al
ways been a puzzling question. This
question does not become any easier
of solution now that in addition to
the luminous nebulae others have
been found which are not luminous,
and whose existence might never
have been suspected IL they had not
obscured other light-giving objects,
or relatively bright areas, behind
; them. Even a family luminous
| background suffices to betray their
presence, as a bat invisible IN COM
plete darkness may be seen as a
shadow If it passes over a dlmly IL
! Illuminated window.
In some places these obscure oo"
jects appear like dark patches upon.
or even like holes in the starry
curtain of the Milky Way. That
they really we're holes, or WIND
| ows," was not long ago a widely
accepted explanation of the more
| sharply defined among them, out
Rarnard's later photographs render
this idea inadmissible. In some
cases, as in the neighborhood or the
| nnhinrhnG the
dark. streaming curtains are signtly
translucent, so that the rays OF some
of the multitude of stars behind
them pierce through.
Then, too, they sometimes appear
to be mingled with, or at least 10
lie adjacent to luminous nebulae, SO
that the conclusion seems irresistible
| that there is an evolutionary relation
| between the two kinds-the dark
nebulae being, most probably, In an
earlier stage than the SHINING ones.
1t would seem that the source OF the
energy which eventually causes the
dark masses to become luminous
If they do-must be in themselves.
Some change takes place which
gives birth to light Or, the radi-
ant energy spreads like a fre in
dry glass from the parts already
incandescent tc others yet dark and
inert Our span OF observation Is
too brief. probably. ever to enable
US actually to see the borders OF p
luminous nebulae expand over the
one, but such an observation, II
made, would be decisive.
The most recent OF Barnard's
photographs are truly amazing in
the definiteness, darkness, and od-
dity Of the forms which they re-
veal. Many of them are relatively
small in area. and these are as
sharply outlined, and as unconven-
tional in shape as, say, the Caspian
Sea. whose queer look on the map
was one of the influences that fired
Humboldt with a desire to explore
the world. A foretaste OF this was
given nearly twenty years ago, but
not rightly interpreted then, by
Keeler's photograph of the great
condemnation of stars and lumi-
nous nebulae called SIN" in the
constellation Sagittarius, where
many curious black spots may be
seen that look somewhat as II drops
of ink had accidently been spilled
pom the photograph.
The luminous gaseous nebulae ex-
;Iibit spectra in which can be dis.
tinguished only three telltale lines.
one Of which has been identified
with the lightest of all the known
chemical elements, hydrogen, while
the others appear to belong to some
rare element or elements unknown
to us
The existence Of an element called
nebuliun. "from its occurrence only
in nebulae, has been conjectured,
and the guess has also been made
that it may be the primal STUFF of
which philosophers have dreamed
for ages, from which all other mat
erial things have been developed.
But the dark nehulae show no spec
ira, because they cannot, since they
give no light. Do they represent the
nrinnal stuff at a still earlier sta zA