The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1883-07-22
NEW THEORY OF THE CORONA.
A Suggestion That IL II an Optical De
IusiOn-ResnIts Of DIR. Has
tings's Observation.

! OF the sun on the 9th OF last May. Taken
as whole, the expedition was a great sue
cess from the scientific standpoint, and also
i'm the pleasure experienced by all the
party. The report says:
1.-THE French party arrived two days
after the Americans. They had steamed
directly from Panama with the hope OF an
ticipating the Americans. Their party
consisted OF NJ. Jansen, NJ. Trouyelot,
formerly Of Cambridge, who made the
wonderful astronomical pictures there; NJ.
Tacchni, the celebrated Italian spectre
scOpst and Secchi's successor; NJ. Pallisa,
OF the Observatory Of Vienna, who is re-
markablc as having discovered more aste-
| roidS than any other man except Peters; a
photographer. and seventeen sailors. IL
rained on the morning OF the eclipse. but
cleared off i'm good time. and the definition
was particularly good. Photographs Occu-
pied the time Of the English and French
observers. Professor Holden and DR.. Dick
son searched for inter Mercurial planets !;
Mr.. Preston took the times Of contact; DR..
Hastings and Mr.. Rockwell devoted their
attention to SpectrOscOpic observations OF
| the corona. No report OF Professor Hold
ems observations has been published fur
| thcr than the statement that they were
negative in their results, no inter-Mercu-
rial planet being discovered. Dr. IIaStingS'S
observations have led to the production OF
Il new theory OF the nature of the corona.
| Briefly stated, the theory Is that the light
seen around the sun during total eclipse
| j. not due to material substance enyelop-
ing the sun. but is a phenomenon OF diff
fraction. From his observations during
| the eclipse OF 1873, made at Central
City. Dr.. Hastings conceived the first
idea OF this explanation OF the solar
corona. Further study served to con-
vince him Of the truth OF this theory, but
he had no means of proving it. Before the
present eclipse, however, he devised n cru
cial test OF his theory. The test is based
on the following already known phenome-
ma: When the moon covers the face OF the
SIM I'M envelope Of light is seen all around
| it: the envelope is not visible when the sun
j. shining on account Of the suns greater
brightness. This light Is called the corona :;
| il i extremely irregular in outline. Ac-
cOrdne to the drawing OF Mr.. j. +. Keel
or ut the eclipse OF 1873. il cnyclOpcd the
sun a> a hazy glow, extending for dis
| tancc Of several minutes OF are from the
suns limb. and at two nearly opposite
points il extended ont in two long stream
prS icathcring of into space. The opinion
has been that this light was due to IN at
moSphcrc extending for millions OF miles
| from the sun. According to DR.. IlaStingS'S
view, il must be light from the sun which
has undergone Tclracton-j. G., has been
| bent from its regular course by the inter-
position OF IN Opaque body like the moon.
"In order to make this plain, suppose
| the front OF il surface Of waves Of any sort
| to be striking an object which rcsi,ts them.
| II an Or"an OF sense is placed in the resist
| ing object il will Judge the direction Of the
waves or the direction Of the object pro-
ducing them by line ut right angles to the
wave front. Now, suppose Il body Is
placed between the object producing the
waves and the sensitive organ. The waves
must 90 around this body. and will pro-
duce an eddy behind it, so that the wave
front will have a different direction, and
| the organ OF sense will conceive the
origin OF the waves to lie in direction
different from that before the body was
| intcrpOsed. Now, consider the waves to
he waves OF light, and their origin the
sun. The organ OF sense IL the retina
OF the eye. The moon is the Opaque body
InterpOSed i'm the course Of the wave, and
they being bent make the impression on
| the eve that the light comes from beyond
the edge OF the sun. The moon covers the
sun during the eclipse and little more,
80 that il can move for about five minutes
and still cover the sun entirely. This
movement i, very slight, and il the corona
consists Of light from solar atmosphere it
should not change at all during this move
mcnt OF the moon. But il dillractiOn is
the cause OF the light then the slightest
change in the relative positions of the sun
and moon should change the contiguratiOn
| Of the corona. e.. the corona should not
remain exactly the same during a total
eclipse. The character Of the light a. shown
bv spectrum analysis should change.
40 determine this point DR.. Hastings
| invented the following instrument: Two
| loZcngc-,hapcd priSmS OF glass were fast
| cred i'm the form Of a letter Y. and so ar
RANGED that all the light falling within the
aperture of the ' was lost. and that falling
on the ends OF the glass pri>mS was trans
mittcd bV series OF reflections to the
apex Of the Y, where the prisms touched :;
here was placed a rcfracting prism, so that
the light could be analyZed. This in>trl-
mcnt was attached To the cyc-piecc OF the
telescope and the image OF the eclipse re-
duccd to such u size that the moon
Just lifted into the aperture OF the ', while
opposite sides Of the corona were reflected
through the prismS TO the place where
they came together. In this way both
sides Of the corona were seen through the
cye-piccc at the same time. On looking at
the eclipse tins j. what DR.. Hastings saw {:
The light Of the corona was divided into
itS constituents. Prominent among them
was a bright green line, which is designa-
ted bv the number 1,47l; to this line at
tcntion was directed. Its presence in the
spectrum has been an argument in favor OF
the view that the corona Is Il solar atmOs-
phere. III this j. the case, the line should
remain fixed during the eclipse; but if the
corona j. due to dilIractiOn, this line should
changc-it should grow shorter in the
light from one side OF the corona and
longer on the other. The observation was
now reduced to watching for change VI
the relative length Of two green lines.
"At the beginning OF tOtality the line
from the west side was much the longer,
but as the eclipse progressed 1t shortened
notably. while the line from The east side,
shorter by about one third at the begin
ming OF the eclipse, grew longer. When
the eclipse ended the proportions OF the
lines were exactly reversed. There had
been change equal to two thirds the
length ofShc lines, while the sun and moon
had only changed their relative position by
an extremely small amount. The only way
in which this phenomenon can be account
ed for i on the diflractiOn theory. The
material view OF the corona will not an
swer for it. But there are other discrep-
ancie, i'm the older view which have been
known far some time. The principal ones
are: |. 1t is known from study OF the
SIN that the gaseous pressure at the
surface must be less than an inch OF mer-
curry, and is probably less than one tenth OF
AN inch, but an atmosphere extending to
fine ,upposeu limits would cause an enor-