Year: 1875

The Eclipse OF the sun.


This highly interesting astronomical event
occurs to-day, and extensive preparations
have been made by our scientific men for the
observation of the phenomenon at several
points where variations in its partial and
annular phases will be apparent The care
ful calculations of astronomers have rem
dered the relative movements of the heavenly
bodies familiar to science The universal
interest displayed in the recent transit of
Venus clearly shows that astronomical re-
search, either regarded as a necessity to our
progress or a scientific luxury, is recognized
by all civilized peoples as afording useful
as well as peaceful field whereon friendly
international rivalries conduce to the general
good. An eclipse of the sun may be briefly
described by stating that it is occasioned by
the complete or partial interposition of the
moons disk between the earth and the sun,
by which the moons shadow is projected on
a part of the earth's surface. This circular
shadow cast by the moon during total
eclipse of the sun is divided into two con-
centric parts of different degrees of dark
ness The inner and darker one is called the
umbra, and is formed by the interception
of the suns direct rays by the moon; the
outer and lighter shadow, or penumbra, is
formed by the interception of the rays tan
genital to the relatively opposite portions of
the circumferences of the sun and moon, and
which converge and intersect in the space
between the two. The orbit of the moon
around the earth is elliptical, like that of the
earth around the sun, and consequently its
distance from the earth varies. When near
enough to the earth to produce total eclipse
Of the sun the moons umbra covers an area
in proportion to its apparent increase of
diameter over that of the sun; but when,
owing to an increased distance from the
earth, the moons apparent diameter is less
than that of the sun, and the disk of the lat
ter is not covered by the concentric disk of
the former, the eclipse assumes an annular
phase, so called from the ring of the suns
bright surface that surrounds the black disk
of the moon, and no umbra is pro-
iected on the earth, neither is the
suns eclipse total The absence of the





the rays which converge from the larger disk
of the sun and are tangental to the moon
meet before they reach the earth The pro-
longation of these imaginary ray lines from
their point Of intersection to the earth's sur
face will embrace the area within which the
ann ular phase of the eclipse is visible; out
side the partial phase of the eclipse becomes
apparent in the crescent form of the un-
covered portion of the suns disk. The
eclipse to-day will be annular and partial.
The annular phase will be visible within q
belt of the earths surface about one hundred
and ten miles wide, and extending from Lake
Ontario southeasterly across the Equator to
Southern Africa. The partial phase will be
visible for a considerable distance to the
north and south of the annular belt Ac-
cording to astronomical calculations the rim
of the penumbra will touch the earth at sun
rise near Bermuda, while the annular phase
will begin at point on the shore of Lake
Ontario. NJ. de Sejour, an eminent French
astronomer, declares that an annular eclipse
of the sun cannot last longer than twelve
minutes twenty-four seconds, total eclipse
not longer than seven minutes fifty-eight
seconds, and that the duration of any eclipse
of the sun cannot exceed two hours. AS the
sun loses none of his light during an eclipse,
and the moons shadow being small when
compared to the surface of our enlightened
hemisphere, total eclipse may be witnessed
in one part of the United States while in
another not even partial eclipse is seen.


AS stated special interest attaches to
this particular eclipse, because it is one of a
series that come only every eighteen years
and eleven days The phenomenon presents
a most beautiful spectacle when viewed from
q central point in the belt where its annular
phase is visible, and affords an excellent op-
portunity for spectroscopic analysis of the
solar protuberances which have long puzzled
our scientific Investigators.