The daily union. [volume] (Washington [D.C.]) 1845-1857, 1846-04-24
To-MoRRoW,s ECLIPSE.

TO-MORROW'S ECLifoE-
To the Editor Of the Union;
| You will oblige the superintendent Of the coast
survey by inserting the enclosed information IN
your paper Of this evening.
| A. A. HUMPHREYS,
Office Coast Survey.
| We understand that arrangements have been
made 10 observe the solar eclipse on Saturday next
in connexion with the coast survey, at the following
named places:
Portland, Maine; Cambridge, Massachusetts;
Nantucket, Massachusetts,; New York, Philadel-
phia, near Annapolis, Maryland
The Boston american Almanac" extends the
calculation to many of the most important points
in the United States. The eclipse begins at WASH
ington at 10 h. "a m 10 s. in the morning. The
greatest observation IL h. Sc m. 9s. The end h.
20 M Is
This mornings Baltimore Sun says that ''the
grand exhibition which is expected to come of to-
morrow will be the last visible eclipse Of the sun
until the year 1854, about eight years from the pres
ent time II will be visible TO the Inhabitants OF
South America north of the equator, the West In
dies, Great Britain, France, Spain, Sweden, the
northwestern portion of Africa, southern part OF
Greenland, Oregon, all the United States, &c. &c;
| IL will begin in annular form, IN latitude ~
| IL south, and longitude 1850 ST. west Of Green.
wich, and so continue TO 20 north and longitude
ll3o west, being distance Of 500 miles, and the
time elapsed will be fourteen minutes; il will then
and there change to total eclipse, and 80 continue
three hours and three minutes and hiny-seven
| seconds travelling in northeastery direction over
a space Of about 200 miles, to latitude 300 ~
north Of Greenwiuh. There the total eclipse will
end, and the annular again commence and continue
for seventeen minutes travelling southwark IN that
line about 100 miles, to latitude $40 56 north, and
| longitude 30 a. west from Greenwich, where It
j will end with the setting sun. The eclipse will COM
mence in Baltimore at 81 minutes past 10 o'clock IN
the morning; the time Of the greatest eclipse will be
SO minutes past III o'clock, and the end % min
utes past o'clock. It's entire duration will be
hours and IS minutes, and its magnitude 100
digts."
| From the Charleston Mercury.
ECLIPSE OF THE SUN.
The approaching eclipse Of the sun on Saturday
the 25th inst induces the writer to offer the follow
ing remarks for the consideration Of these who take
| pleasure in the study Of astronomy
The general principles Of the theory OF ecllpses,
and the particular uncture Of circumstances under
which they occur, are Familiarity known that
eclipses only happen at new and full mooni that the
path which the moon pursues in the heavens IL not
coincdent with that which the describes during
the year. that the former is inclined TO the latter at
an angle Of about degrees, and intersects At at two
opposite points called the nodes; that, consequently,
eclpses cannot happen at every new and full moon,
but only when the sun is al one Of the nodes
We need not therefore, dwell further them, but
propose TO show in the present article that the num-
Der Of eclpses that occur IN year cannot be more
than seven nor less than two, although by no means
all Of these are visible at any given place.
Since eclipses only happen when the sun is
near a node, there must be limit to his distance
from the node, within which limit eclipses might
happen, and beyond which they could not occur;
this distance is found TO be- for ecpses Of the sun,
II deg for eclipses Of the moon, ~ deg. To state
this distinctly: if at the time Of any new moon the
sun be more than II deg. from Of the nodes, no
place the surface OF the earth will see the
eclpsed; il he be less than II deg from the node,
some place may see him eclpsed. In like manner,
If at any full moon the sun be more than IL deg.
from one Of the nodes and consequently the earth's
shadow more than IL deg. from the opposite node,
near which, of course, the moon must be, the moon
| will pass above or below the shadow without en-
tering it, and there will be eclipse; if the sun be
less than - deg. from node, an eclipse may hap
pen. This space Of "a deg-l7 on each side Of a
models called the solar ecliptic limit the space Of
"a deg-l2 on each sde-s the lunar ecliptic limit.
| Now since the sun describes his annual circuit
of the heavens, $50 deg, in 365 days, he moves a.
the average rate Of about deg. in day, and would
describe the solar eclptc limit In interval Of "a
days. and the lunar in "a days; also since the
interval between the two successive new two sue
cessive full moons is about 30 days, in any given in
terval Of "a days new moon must occur, and hco
| new moons may, and during any given interval OF
| "a days, one full moon may happen, and possibly
none 1t follows therefore that while the sun is passing
through the solar ecliptic limit solar eclipse must
happen, and ioo may, but not more; and that while
he passing the lunar limit, lunar eclipse may
| happen, and possibly The nodes being in
opposite points Of the heavens, the sun having
passed one Of them, will pass the other about six
L a. "a k,.L IL.
cur. There, therefore, must be at least tco solar
eclipses every year, and possibly lunar eclipse at
all Such is the case the present year. II an eclipse
Of the sun happened early in January, followed by
another at the succeeding new moon, two similar ones
may be expected six months after, being the third
| and fourth, and IL revolutions Of the moon
accomplished in IL days short Of ~ months a
year, another solar eclipse might happen before the
close of the year, making five in ALL the greatest
| number possible ina year. In like manner if an
eclipse of the moon happened early in January,
another might occur about six months after, and a
third late in December making three in ALL the great
est number possible in year.
| When two solar ecipses occur at two successive
new moons, sometimes called twin eclipses, there
must be a total lunar eclipse at the intermediate
| full moon; because, twin eclipses happening when
the sun at the first new moon is approaching the
node, and Just within the solar ecptic limit, about
Is deg, for example, from the node, and at the next
being only about is deg. from it is yet within the
limit the sun must be at the immediate full moon,
IS days after the first new moon, at or very near
the node, and there must consequently be a total
eclipse of the moon. Therefore, when there are
five solar eclipses in year, there must also be too
total lunar ones, making ecpses of both kinds.
IT. however, one Of these intermediate total lunar
eclipses should early in January, then there
might be three lunar and four solar, making again
sepen in ALL the greatest number of both kinds pos
sble in year.
To sum these results:
There cannot be more than FIVE solar eclipses in
a year, nor less than two.
There cannot be than three lunar eclipses in
a year, there may be none.
There cannot be more than seven Of both kinds,
FIVE of the and two of the moon or four 81
the sun and three Of the moon.
In l84l, there were echpses of the sun, and Of
the moon; no current year has presented seven
eclipses for some time past, although of course it
has happened that eclipses have occurred within
the space Of 1865 days. The year 1893, is the last