Memphis daily appeal. [volume] (Memphis, Tenn.) 1847-1886, 1869-08-07
THE ECLIPSE TO-DAY
Preparations for Scientific 0bserva-
tons during the Transit.

The total eclipse OF h sun, which
will be visible to-day over a belt of
country about 40 miles broad, and
stretching from Alaska to North
Carolina, bids fair to be more thor
oughly observed and utilized in the
cause of science than any similar
phenomenon heretofore. Numerous
parties have been organized to make
astronomical, physical and photogra-
phic observations, and will be located
along the central line which passes
through or near BoonesbOro, Des
Moines, Burlington, Iowa; Spring
field and Shelbyville, Illinois; Bruce
vile and Newton, Indiana; Louis
vile, Mount Vernon and Manchester,
Kentucky; Bristol and Estivilie, Vir-
ginia; Union, hingsport and Blounts-
vile, Tennessee; Wilkesboro, LeXing-
ton, Fayetteville, Clinton and Lees
burg, North Carolina.
OF these parties the largest and
most complete in its appointments
will be that organized in Philadel-
pEia, by Prof. Henry Morton, under
the authority of Prof. J. II. C. Cofip,
who has in chargethe appropriation of
a part of the fund voted by Congress
for making such observations. This
party will be essentially q phOtOgra-
phic one. There have been secured
for its use the equatorial belonging to
the Philadelphia High School, of six
inch aperture and nine feet focal
length, provided with clOck-work
driver; also twin instrument belong
ing to the Pennsylvania College at
Gettysburg, and a smaller tei scope,
e%quatOrially mounted, but without
clOck-wOrk, belonging to the Univer-
sity of Pennysvlvani. All these in
struments have been fitted by Mr..
Joseph Teutmayer with special eye
pieces, instantaneous exposing slides
and cameras, and are now deposited
in a temporary building in West
Philadelphia, in a most convenient
location, placed at the disposal of the
party.
Preliminary experiments are now
in progress, and some excellent re-
suits have been already reached.
Thus, pictures Of the suns disk, two
and a half inches in diameter, have
been taken, showing the numerous
spots or dark markings with which
our luminary abounds at regularly
recurring periods of eleven years, of
which this one, as well as the facul8
or luminous cloud-like markings
which are always found oyer his sur
face, and show especially towards the
edge Of his disk.
The exceeding shOrtness of exposure
for these pictures is a curious feature.
The act of exposing 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 it, one-fortieth
of an inch wide. This plate is held
up by a trigger so as to cut off tine
light, and is pulled down by a stiff
spring. When the trigger is lightly
touched it releases the plate, which
then flashes across, allowing the light
TO pass on to the sensitive plate only
during that instant of time occupied
by the narrow opening (of one
f0rtieth of an inch in passing across
the center line of the tube. So power
full, however, is even this mOmentary
flash that it was found necessary to
cover up the lens of the telescope, all
except an opening of an inch and a
half in the center, thus reducing the
amount of light which entered to one
sixteenth of what would have passed
the full aperture of six inches.
The destination Of this party-or,
rather, this collection of three par
ties-is Burlington, Iowa, and its Vi
cinity. That point is selected because
it is the best situated of those which
are equally accessible. The further
west we 90 the earlier in the day will
! the eclipse occur until we reach Alas
ka, where it comes about noon This
is both on account of the difference of
apparent time lit being at the same
actual moment sunset on our Atlantic
| coast and near noon On the Pacitic),
and because the moon travels over the
sun from west to east, so that it takes
nearly two hours of actual time for
the shadow to traverse our Continent.
The nearer TO noon the phenomena
occur the better for observations, eS-
pecially Photographic ones, as there is
less risk of haze or cloud about the
sun. The duration of the total phase
L also longer where the eclipse occurs
at noon; fer then the surface of the
earth is moving nearly in the same
| direction as the moon and itS shadow,
and so tends to keep in the shade
longer. Near sunrise or sunset the
surface Of the earth would be simply
moving toward or from the moon,
and this motion (of one thousand
miles an hour would therefore have
no effect in keeping up with the NOV
ing shadow. The duration of the en-
tire eclipse, from first to last contact,
will be 8bOGt tyO hours.
Besides the telescopes and photo
graphic arrangements, electric elr0-
nographs will be taken by this party,
which will be. so connected with the
telescopes that each exposure will be
automatically recorded TO the fraction
! Of 3 second, and thus such a series of
permape4t observations will be Sc
cured as are Without 4 parallel in the
history of astronomy. So large "a
number III observers and so much APP
paratus could not have been brought
on the field on the strength of the
Government appropriation alone had
il not been for the kindness of Mr..
Thomas Scott, of the Pennsylvania
Central Railroad, who has provided
free transportation to this entire party,
with their apparatus, Ia gpeciQlcaI to
their destination. To the expedition
this assistance Is equivalent to a dOub-
ling of the Government grant, and
with the aid afforded to other parties,
raises this munificent donation to an
equality with the entire appropriation
OF the British Government to the ex-
petition of De la Rue to Spain during
the eclipse of 1860.