Evening star. [volume] (Washington, D.C.) 1854-1972, 1889-12-14

eclipse. but it is probable that at those places
the horizon, where the sun will be when the
eclipse occurs, will be obscured by the mists of
morning. 1t is desirable to note the eclipse when
the sun Is high in the heavens when he is
free from interference. and SO the astronomers
selected the western coast of Africa the OBJ
lectlve point of their expedition. Had there
been some chance island in the ocean directly
in the line of totality it might have been util-
lied, but unfortunately there is nothing on the
map that looks like solid ground anywhere be-
tween the Brazilian cape and
ST. PAUL DE LoANDo.
IN the immediate vicinity of the black line, and
after they get there what do they do? That is
complex question to answer They have a
ship load of instruments telescopes, spectre
scopes. Photographic cameras and scores of
other implements. with which they VIII utilize
every one of the lS7 seconds when the sun is OBJ
scured. In order to obtain the most satisfactory
results possible 1t Is probable that each obser-
Walton will be duplicated by different Observers
as lar as the number of instruments will per-
mt. 1t is this variety of sources that gives the
data OBTAINED from an eclipse its peculiar value
IL may be stated as an axiom that an astronom-
zeal truth cannot be said to be established I'M
I'll Two persons, working independently, have
OBTAINED the same results.
WHY ECLIPsEs ARE OBSERVED.
The main object nowadays in viewing ecipses
is to obtain new light on the subject of the
nature and extent of the corona, the bright
efulgence which is seen surrounding the suns
disk at the moment of totality. As soon as the
DIlndlng rays are shut Off by the medium of the
moon this halo appears. 1t is an uncertain
quantity IN size as well character for it varies
tremendously in different eclipses There is
brst a very bright rim of light lying close to
the dark edge of the moon, then the flames
take definite shape and shoot off into space to
enormous distances.
PHOTOGRAPHIC AN ECLIPSE.
These things are noted by means of an ordi-
nary Photographic camera attached to a strong
telescope lens. A clockwork keeps the appa-
ratus moving in unison with the motion of the
earth, so that the obscured sun is kept in the
field of the lens throughout the period of to-
tally. Successive photographs are taken, each
instrument thus producing a series of plates
You have, OF course, noted" said q local
astronomer to a STAR reporter. THAT when you
go IRON light room into dark one you are
temporarily blinded, and it takes an apprecia-
BILE time to recover the full use of your eyes,
SO 1t Is necessary for the observer to blindfold
his eyes for few minutes just before totality
in order to lose no lime recovering the power
of seeing clearly"
The spectroscope is also attached to a pho
Geographic apparatus and pictures are taken of
the story which the prisms tell about the kind
of light emitted by the sun and its appendages
The observations so far taken by camera and
spectroscope have gone far toward proving
that the corona is an atmospheric appendage
to the sun in the form of glowing gas, swing
ing and whirllng around the planet into space.
THE suns SURROUNDINGS.
Prof. Proctor has said: studying the suns
surroundings we find his complex atmosphere
to be some 300 or 400 miles deep. the sierra
from 5000 TO 5000 miles deep. the prominence
region about 100000 miles deep. though occa-
sional outbursts to twice that height have been
observed. The inner corona seems to be some
10000 miles, the outer about 100000 miles in
height, measured from the suns surface
Lastly, there coronal streamers which
have been traced to distance of
100000 miles, but may in reality extend
much further, while the zodlacal traced in
eclipse 10 distance of 10000 900 miles, and dur
ing morning and evening twilight to nine times
that distance, occupies in reality most probably
region coeXtenslye with the solar system it.
self" The sierra of which he speaks is a low
lying line of intense red light visible during an
eclipse, due to lncandesceut hydrogen Ii has
lately been observed by astronomers at ordi-
nary times by the spectroScope. The red promi-
neuces are projections of the sierra.
Edison, the American electrician, has in
vented machine to test the heat given forth
from the corona during an eclipse and July
%. 1878. he took observations in the hope of
determining its quantity. 1t was SO delicate,
however, that the indicator finger moved out
of the scale.
ON the ed a number of photographs will be
taken of the eclipse itself as we'll as of the
spectra OF the corona and the red prominences.
Measurements and comparisons will then be
taken and some formulation made of the re-
suits.
At the National observatory in this CITY the
outcome of the expedition is being watched
with intense interest By all the astronomers.
SAID one OF them the other day to THE STAR
reporter:
Il hope that they will accomplish something,
put am afraid that they have undertaken a
little too much. 1t is far better in such an ex-
petition to limit the field of work directly to
the observation OF the unknown quantities. |
hope that they will make some notes on the
lines thrown in the spectrum by
the red prominences, which appear dark
when the sun is unobscured and re-
verse to light just at the instant the surface
IS wholly covered 1t was planned at first to
take series OF photographs of the spectra of
this reversing process, but am not sure that
they will do it. 1t seems that it was first
agreed that the party should go into the
interior couple of hundred miles in
order to reach high ground in the field
OF totality, but 1 believe that they have
changed this plan and intend to remain
near the coast. They took instruments from
this institution, from the coast and geodetic
survey, from nearly all the colleges fir ON the
national museum, and, in fact, from almost
every source within reach, and am told that a
large part OF the collection was left on the
wharf at the Brooklyn navy yard. You must re-
member that they have gone all the way to
Africa in the hope that the 22d will be clear
day. 1t will be rather rough if it rains won't
It!"