Martinsburg herald. [volume] (Martinsburg, W. Va.) 1881-1920, 1900-05-26

| Of the moon being such that 1t permits
us to see almost to the very limb Of
/ the sun itself. In the coming eclipse
the diameter of the shadow across the
gulf and Atlantic states Is between 10
and 30 miles. Within this region no
direct sunlight can penetrate so long
as the shadow is passing. The heavens
would therefore be as dark as night
were Il not for light reflected into the
shadow from the atmosphere outside
Of II, where the sun still shines In
the present case there will probably be
much more light than during ecIipses
Of very long duration. Still the amount
Is almost indnitesimal in comparison
with that ordinarily shed by the direct
rays Of the sun
To understand the problems which
our observers expect 10 attack some
thing must be said about the surround
ngs Of the sun. To all ordinary OBJ
seryation the latter Is simply a shining
globe, with no visible appendage. Nei-
Their by photography nor by the most
careful scrutiny with powerful tele-
scopes has the astronomer ever been
able to perceive any object outside the
surface Of this shining sphere. But by
observations during total eclipses it
has been shown TO have several APP
pendages. Lowest down, Immediately
resting on the surface of the sun, is a
sort of solar atmosphere, red In color,
OF the upper part of which hydrogen
is one of the principal constituents.
This is known as the chromosphere.
Lower down, resting Immediately on
the solar surface, the chromosphere
comprises a layer of gases composed of
the vaDors of most of the common sub
stances known to exist on the earth
and In the sun. So intense Is the heat
that these substances are not only
melted, but actually evaporated, as
water would be evaporated over hot
fire. This part of the chromosphere is
called the reversing layer. The hydro
gen of the chromosphere is piled up in
huge, irregular masses of every shape.
These are seen during the total phase
as rosy prominences, apparently scat
tered round the dark body of the moon
here and there. Sometimes they have
the appearance of cloudlike masses,
sometimes of immense flames shot up
to height of many thousand miles
from the solar surface. Surrounding
the entire sun. chromosphere and pro-
tuberances is the soft effulgence known
as the solar corona. These three OBJ
jects, chromosphere, protuberances and
corona, are the more or less mysterious
appendages of the sun the nature and
constitution of which give rise to some
of the most difficult and interesting
problems of solar physics.
The discovery of the reversing layer
was the work of Professor Young dur
ing the eclipse of 1870 in Spain. 1t is
therefore sometimes called Young's
stratum. 1t is seen only when the to-
tai phase is beginning or ending. TO
understand it's significance we recall
that the solar spectrum is always
crossed by number of dark lines pro-
duced by the absorption of certain
rays by the solar atmosphere. Young,
observing this spectrum as the moon
was about to completely hide the sun,
noticed that as the last ray of true
sunlight disappeared the spectral lines
were suddenly changed from dark to
bright. For n moment hundreds of
these bright lines flashed out. then
disappeared as suddenly as they had
appeared. The same gases which, by
absorbing the sunlight which passed
through them, caused dark lines to
appear in the spectrum were hot
10 ,sixr mi, hp
sunlight was cut off.
The introduction of Photographic
methods into astronomy has initiated
a revolution in the method of Observ
ing total eclipses which will see its
completion on the coming occasion.
Up to recent period the observations
were necessarily purely visual OBJ
servers drew pictures of the corona as
they saw 1t or fancied it. The promi-
nences were delineated as they could
be seen during the brief period ayaila-
bic for the purpose and the lines of the
spectrum were observed by the eye.
The application of photography to the
phenomena of a total eclipse is almost
as old as the art itself. But with the
y
were of little Importance. Now, how
ever, the astronomer is not going to
trust to his eye, except where it cannot
well be helped. Everything that light
can depict ON Il sensitive plate viii be
iudellbly recorded in such a way as to
be free from all the illusions Of ordi-
nary vision and will be studied at lei
sure by the best eyes with the most
refined apparatus.
An idea Of the great advance thus
made will be gained from the fact that
in few seconds as much of the corona
can he photographed as it is possible
for the eye to see by looking directly
nj il, This will be the case even with
Youug's reversing layer, 1t is expect
cd that during the moment Of its WISH
/ hility lines win be photographed which
| the eye cannot possibly recognize in so
! brief an interval Those astronomers
viii get the best chance at this inter-