The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1869-08-04

| tional motion in its orbit of $4,000 miles per
hour to the west! The moon is revolving
around the earth at the rate of about 2000 miles
| per hour from west to cast. 1t is plain, there
! fore, that the cone-like shadow OF the moon,
which Mt the coming eclipse will be 10 miles in
! diameter, cannot and does not remain long on
| the same part of the earths surface. For the
moon is flying around the earth in her orbit from
west to east with the velocity, on the 7th of
August of about 40 miles per minute; and the
| shadow passes over the carths curved surface
with the increased velocity of about a miles
per minute or nearly thrce-Quartors of . mile
| every second of time Hence the whole
circular shadow, of one hundred and
forty miles diameter, sweeps over the earth, in
| general direction from the west towards the
east, forming belt of its own width, more than
| six thousand miles long, in the short time of
| about two hours and half. The penumbra
covers circular space Of 1900 miles in diameter,
the eclipse happening exactly at thenode. Thus,
| the axis of the shadow is inclined to the plane
of the ecliptc, the shadow viii be cut oblquely,
and that part of the earth in the shade will be
oval. Such chart as the spectator would OBJ
serve from outside of the EARTH and the astrono-
mer compile by calculation, is presented in
! Figure 2.
If that cut be compared, as the parallels Of lati
| tude and longitude allow, with large map of
| the United States, it will be found that the CEN
| tral line of the path of the umbra enters the
territory of the United States about two hundred
miles northwest of Fort Union, which is situated
| at the junction of the Yellowstone and the Mis-
souri, rivers. 1t sweeps southeast across the
| Territory of Dacotah and enters the State of
Iowa near its northwestern boundary, near Lin
coin, at 4'29 p. NJ. The gigantic wings of dark
ness, 140miles broad, will sweep across the whole
| length of Iowa in less than thirty minutes.
Springfield Illinois, will be enshrouded at sos
! p. NJ, Vincennes Indiana, at 515 Louisville,
Kentucky, at 5'25, Abingdon, Virginia, at 5'42,
Morgantown, North Carolina, at 5'44, and at 65
the corona of glory will be reflected in the lbil-
lows of the Atlantic dashing upon the isets of
that State.
Its Phases in Philadelphia.
Neither corona nor rOsy-hued flames nor CO.
ruscated rosaries of beads will be visible to the
good dwellers in Philadelphia. The ill-condi-
toned kline left to browse on the scanty herbage
of commons will not chew the cud of wonder;
the grunters left to run loose among piles of
[ bricks and mortar, and half-built houses and I'M
savory garbage, will not homeward plod their
weary way on a doubled trot; the roosters
penned up in city cellars will not huzzah out
their cock-a-doodle- as the sun Just sinks
| below the horizon. None of these wondrous
| things will be witnessed by our citizens, for
Philadelphia will not be deprived of all her sun
light on that occasion. Attention to the follow
ing hints, however, will, if the weather permit
enable the partial eclipse to be enjoyed as it
well deserves to be:-
Where nothing better can be had, a bit of
plain glass, smoked over candle or lamp,
in some parts more deeply shaded than
in others, to suit the varying intensity of the
-.
I will enable the observer to see most of the phe-
nomena. In the city it will be easy to procure
pieces of the red or ruby-tintcd glass, of diff
ferent shades or depths from most of the gla-
ziers, which may be used with advantage, in
stead of the smoked glass Those who can
command a good opera-glass, or small telescope
| of any kind, provided with shade glass to
screen the eye, will of course have a better view
To those whose eyes require caution in using
and to others for variety sake, it will pay to take
a large card with small round hole in the CEN
tre and hold it against the suns rays, so that
the shadow will fall on the floor pavement
wall, or other dark and smooth surface. In the
middle of the shadow there will be a true image
of the sun, and the eclipse can be stu
died in its progress without strain
ing the eyes, and without shutting face or
hands with smoked glass. This simple process
that the light spots in the shadows during a
solar eclipse take the shape Of the luminous
portions of the suns disc, and the perforated
card has been used with perfect success.
Points of Observation.
The exact astronomical figures of interest to
this city as follows-The eclipse begins at
5h. SO P. M; it is greatest at Oh. 51m.; it ends
at Oh. 57'6m. Its duration will be In. 49m.; its
magnitude 1915 digits Ga total eclipse being and
its pointof beginning 132 deg. The south side will
be eclpsed. Applied practically in observation,
all the above calculations are valuable, as they
direct the attention to the exact time and point
of the commencement of the partial obscuration
Let the spectator, while looking at the de-
clining sun, imagine straight line drawn
through the sun from top to bottom, and another
through the middle from right to left, as if it
were to be sliced into quarters like an apple.
The upper point of the line will be 0 deg the
right hand point-of course as the person must
be facing to the west, his right hand will be
towards the north-will be 80 deg and the
lowermost point lS0 deg. Midway between the
latter two points may be inserted 135 deg; at
this point practically the first observation will
be visible. The line of shade will creep pro
dually up over the disc of the sun, covering the
lower limb regularly in its progress. At its
greatest observation, about eleven-twelfths of
the suns surface will be darkened and tbe
small rim unobscured will be the upper section
of its disc AS the sun sets on Saturday at 7.6
about ten minutes will eiapse between the end
ing of the eclipse and the sinking of the sun