The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1893-04-09
THE COMING ECLIPSE.
Extraordinary Preparations for Photo
graphing the Corona
BY Professor c. A. Young, PRINCETON
College Observa-
tory.

PRINCETON, N. j., April Just now
the interest of astronomers is very much
taken up with the total eclipse of the sun,
which is to occur on April is.
The shadow which, like long black
tail, extends nearly 100000 miles behind
the moon, VIII then brush its tip across
the face Of mother earth, first touching
the Pacific ocean of the coast of Chill,
traversing the whole width of South
America, crossing the Atlantic and final
II leaving the globe in the middle Of the
Ozark Continent Wherever 1t touches
there will be a circle ct darkness. varying
in width from so to l20 miles, and II will
move with speed exceeding that OF a
cannon ball, occupying from three
minutes to four and quarters In
passing over any spot which is upon the
center of its track. The fortunate OBJ
server so situated viii, if the weather is
fine, witness the wonders OF a total
eclipse.
The moon viii appear to first strike the
western edge OF the sun, and little by lit
lie Will encroach upon IL until the whole
OF the blazing disk is covered. Then,
while the shadow is passing, the scarlet
chromOSphere, the sO-called prom
nences.'s and above all the mysterious
corona, the most beautiful OF all the ce-
lestial objects, VIII become visible for
few brief moments, until the sunlight
again breaks forth.
On such occasions the exact moments
when the moons edge first touches and
finally leaves the sun, and when 'total-
ity'' begins and ends are carefully noted,
since such observations, made at known
stations. are of great value in determining
the InOun's place and motion. But at
present still greater interest attaches to
10 the castro physical observations
farrr
seconds of total obscuratlon-o observations
with spectroscopes, photometers, polar1-
scopes, and especially with Photographic
apparatus of various kinds.
With the spectroscope the observers
viii try TO study the peculiar phenomena
which accompany the beginning and
close Of totality, when for an instant the
familiar dark-lined spectrum OF the sun
is transformed, and is filled with lines
that are bright instead of dark; lines
which, thoroughly observed and identi-
fed, would yield most instructive
record of the constitution of the solar sur
face, and settle instantly long docket of
disputed questions.
But the visual observations are ueces-
sarily hurried and difficult and afford
great scope for personal bias. If the pho
Geographic plate can be made to register
the heeting facts-and the attempt will
be made on this occasion with better
then the record, if less complete than
that given by ocular observations. will be
more certain and trustworthy. Hitherto,
1t is true, photography has not been very
successful In dealing with this phenome-
non, but since the last attempt the instru-
ments and plates which are to be used
have greatly improved.
EDuring the three or four minutes be-
tween the critical instants at the begin
ming and ending OF the tOtality, the
spectroscopists will be busy with the
prominences and the corona, seeking to
utilize the advantageous circumstances to
obtain some new information as to their
constitution and physical condition; and
in this mere deliberate work there is no
question that photography Will be most
successfully employed.
There are a number of problems con-
nected with the absolute and relative
brightness of different parts of the corona.
and polarization of its light, and these
will occupy the photometers and polari-
scopes.
But the most prominent part of all in
the observations of the eclipse will be
taken by photography. AS already init
mated, many OF the Epectroscopes will
work photographically; but besides this
there Will be a multitude of cameras of
various construction designed to obtain
pictures of the corona and prominences;
some of them are planned for the detailed
study of details on large scale, others to
secure pictures of the whole extent of the
corona with its faintest outlying stream
ers. Some OF them use rejecting TELESCOPES, /
some refracting telescopes OF the ordinary
construction, and some are large CAM
eras with specially constructed combina-
tons of lenses. Some of them employ
plates sensitive only to the invisible ul-
tra-violet rays which are peculiarly
abundant in the light of the corona.
OH
giving picture more nearly resembling
what is seen by the human eye. At
present the study Of the corona consti-
tutes distinctly the main object of eclipse
observations, because the phenomenon,
in itself. is so beautiful and wonderful,
is so imperiectly understood, and because
while all other solar phenomena are at all
times more or less accessible to modern
methods of observation, this alone can be
observed only while the sun is hidden by
the moon.
A large number of parties are now on
their way to observe the eclipse at various
points in South America and Africa.
There is no government expedition from
the United States, but two small parties
go from this country TO Chill. One of
them is under the charge OF Prof. Schae-
berle of the Lick university, and takes an
outfit almost wholly Photographic, de-
voted entirely to the study of the struc-
ture and extent Of the corona. The OBJ
servations are to be made fifty or sixty
miles inland, at an elevation of 1900 or
5000 feet, so as to avoid the haze which in
the early morning usually envelops the
coast at this season of the year. Another
party, hailing from Harvard observatory
is in charge of Mr.. Bailey, who had q
long experience in astronomical pho
Biography in California and Peru. 1t is
quite possible that his party may be
Joined by Professor w. n. Pickering
fbrother OF the director of the Cambridge
observatory from Arequipa, where the
new Boy6en Fund observatory is being