Evening star. [volume] (Washington, D.C.) 1854-1972, 1869-08-03
The Eclipse Of Angus, =, 1869

The total eclipse OF the sun, which will be
visible on Saturday next over q belt OF country
Alaska 70 North Carolina, bids fair to be more
thoroughly observed and utilized in the cause
Of science than any similar phenomenon here
tofore. Numerous parties have been organized
TO make astronomical, physical and photo
graphic observations, and will be located
along the central line which passes through
or near Boonesboro, Des Moines. Darlington,
Iowa; Springfield and Shelbyville, Illinois:
Bruceville and Newton, Indiana; Louisville,
Mount Vernon and Manchester, Kentucky;
Bristol and EstlivIlle, Virginia; UEiou, Kings
Lexington. Fayetteville, Clinton and Leesburg
North Carolina.
OF these parties the largest and most COM
plete in its appointments will be that organized
in Philadelphia, by Professor Henry Morton,
under the authority of Professor j. II. e..
Coffin, who has In charge the appropriation of
part ofthe fund voted by Congress for making
TALLY Photographic one. There have been
secured for Its use the equatorial belonging TO
the philadelphia High School, Of six feet
aperture and nine feet local length, provided
with clockwork driver; also q twin instrument
belonging 10 the Pennsylvania college at
Gettysburg, and a smaller telescope, equatori.
ally mounted, but without clock work, belong
Ing 10 the University Of Pennsylvania. All
these instruments have been fitted by Mr.
Joseph Teuunayer with special eye pieces, in =
stantaneous exposing slides and cameras, and
are now deposited IN temporary building in
West Philadelphia, in a most convenient loca-
ton, placed at the disposal OF the party.
Preliminary experiments are now IN pro-
gress, and some excellent results have been
already reached. Thus, pictures of the suns
disk, two and a half inches In diameter, nave
been taken, showing the numerous spots or
dark markings with which our luminary
abounds at regularly recurring periods of
eleven years, Of which this is one, as we'll as
the faculI or luminous cloud-like markings
which are always found over his sur ice, aud
show especially towards the edge OF has disk
The exceeding shortness ofexposure for these
pictures Is q curious feature. The act of ex-
posing Is managed in the following manner
On the front OF the camera box, at the lower
end OF the telescope, Is a narrow opening across
the tube, in which slides a plate of brass with
a slit across II, one-fortieth Of an inch WIDE
This plate is held up by trigger SO as TO cut
on the lighr, and is pulled down by a stiff
spring. When the trigger is lightly touched il
releases the plate, which then flashes across,
plate only during thar instant of time occupied
by the narrow opening (of one.fOrtieth of an
inch) in passing across the centre line of the
tuoe. 50 powerful, however. is even this mo-
mentary flash that 1t was found necessary 70
cover up the lens OF the teles COPE all except an
opening Of an inch and q half in the centre
tn reducing the amount Of light which enter
ed to one-sixteenth of what would have passed
the full aperture OF six inches.
Inc destination OF tnis party-or, rather. this
collection OF three parties-is Burlington,
because il is the best situated of those which
are equally accessible. The further west we
go the earlier in the day W i'll the eclipse occur
until VI reach ALASKA, where il Genes about
noon. This rs both on account of the difference
OF apparent time (1t being AT the same actual
moment sunset on cur Atlantic coast and near
noon on the PacificD aud because the moon
travels over the sun from west TO east so that
II takes nearly two hours of actual time for the
shadow to traverse our continent. The nearer
10 noon the phenomena occurs the better for
observations, especially Photographic ones as
there is less risk OF haze or cloud about the
sun. The duration of the total phase is also
longer where the eclipse occurs at noon: for
then the surface OF the earth is moving nearly
IN the same direction as the moon and its shad-
ow, and so tends 70 keep in the shade longer
Near sunrise or sunset the surface OF the ca rth
would be simply moving toward or frem the
moon, and this motion (of one thousand miles
an hour) would therefore have no effect i'm
keeping mp with the moving shadow. Thedu-
ration OF the entire eclipse, from first to last
contact, will be about two hours.
Besides the telescopes and phonographic
arrangements. electric chronographs will be
taken by TINS party, which will be so connected
with tne telescopes that each ex posure will he
AUTOMATICALLY recorded 10 the fraction of a
second, and thus such a series of permanent
observations Will be secured as are without a
parallel In the history of astronomy. So large
number OF observers and so much apparatus
could not have been brought on the field on the
strength OF the Government appropriation
alone, had II not been for the kindness of Mr..
Thomas Scott, OF the Pennsylvania Central
Railroad, W no has provided free transportation
lor, TINS entire party, with their apparatus, in
q special car TO their destination. 70 the expe.
dition this assistance lie equivalent to doubling
OF the Government grant, and with the aid
anorded TO other parties, raises this munificept Z
donation TO an equality with the entire appro-
priation OF the British Government to the expe-
diuon OF De ia hue 10 Spain during the eclipse