Year: 1874

the time or IuH moon On sunday morning 70 eS-
cape total immersion In our shadow. 1t is evi-
dent that the chances OF passing through the
shadow depend greatly upon the size OF che
shadow at the point through which 1t passes.
And here we see the explanation OF the compara-
tive number OF solar and lunar eclpses. By refer
ence to the diagram 1t will De seen that at any
time when the moon is between the extreme
outer lines connecting the sun and earth, and to
the left OF the EARTH there will be eclipse OF the
sun visible somewhere on the earth. In tact, this
circle is 80 large that the moon cannot avoid
passing through 1t at least twice every year. But
on the right OF the earth these lines converge into
very much smaller circle, and frequently
whole year passes by without the
moons once touching that circle. Never
tneess, as in the former case, the eclipse
OF the sun may be visible only In the neighbornood
OF the North or South Pole, where there are fe v,
II any. observers, and az in the latter case the
eclipse OF the moon will be visible wherever the
moon can be seen, which includes tine whole
hemisphere Of the earth turned toward II; a n
eclipse OF the moon is much more frequently wit
messed by any particular individual or at any par
ucular place. than an eclipse OF the sun.


WHAT THE DIAGRAM SHOWS.


The diagram represents the moon, to the right
OF the earth, at one O'Clock on sunday NOR ming,
just as 1t is entering the earths shadow. 1t is





the light OF the sun Is so intense that while any
portion OF 1t can shine directly upon the moon
its briliancy Is not much diminished.
Thus far We have entirely omitted to con-
slider the eject OF the earths atmosphere. The
light from the sun that passes the edge OF the
earth Is bent inwards on each side by the reirac
ton Of our atmosphere, causing 1t to come to
point much nearer the earth. The rays passing
nearest the earth, which are most refrscted, come
10 point AZ about rwo-thirds the moons distance
from the earth, and the rays passing higher come
to point at greater distance extending all the
way out to the end Of the shadow represented.


HOW THE NOON WILL LOOK.


Even when the moon is In the centre OF the
shadow, therefore, It il always illuminated by .
dinused light from the sun, usually SUFFICIENT to
make II easily visible As the setting sun appears
red, from the earth's atmosphere cutting of the
blue rays and as 1t is exactly that red light which
falls upon the moon, II is usually observed Of .
reddish color, sometimes even OF glowing
red. In the present instance the moon passes so
near the edge OF the shadow that the whole OF this
refractcd light will fall upon It, even from the upper
strata Of our atmosphere, and hence we may
reasonably expect the moon to be easily seen but
it's color win depend SO much upon the condition
OF the weather in those parts OF the earth through
which this light passes that IL is impossible to pre-





our Arctic circle would probably make it glowing
red, while clear atmosphere above. especially If
combined with dense clouds near the surface Of
the earth, would probably make it appear nearly
white.


In the smaller figures. under the large cut re-
presenting the appearance Of the shadow upon
the moons disk.-nrst, at the beginning OF the
eclipse; second, just before 1t becomes total;
third, just after 1t ceases to be total and fourth,
Just before the eclipse ends-it will be observed
that the line representing the moons axis, con-
Meeting its north and south poles, is inclined TO-
ward the right. There are three causes for this.
If the moon moved In the plane or the
earth's equator and were In the meridian
at the moment OF observation the axis
would be vertical; but as it moves
nearly In the ecilprc (which Is the plane OF the
earth's orbit, and as 1t Is situated in portion OF
the ecliptc which is rising above the equator as IL
Is moving toward the left, this incllnes the axis
about twenty degrees toward the right The
moons orbit being itself inclined five degrees TO
the ecptic, and the moon being 1t the time OF the
eclipse near its ascending node where it rises
most rapidly from the eciiptic tnat increases the
inclination to the right to twenty-five degrees
But the greater part OF the inclination depends
upon the angle OF the equator itself with the hor-
izon. This inclination 10 well shown by the daily
motion OF tne sun, moving, as IL rises, IN an o0-
lique line upward and to the right, the line be-
coming gradually more nearly horizontal, UNTIL in
the south, II IL exactly horizontal. The sun then
begins to descend. and the line becomes more and
more obliqus, until it sets at an angle OF about
ffty degrees The moon having already passed
the meridian when the eclipse begins, its axis is
inclined sttll more from the inclination OF the
equator 10 the horizon. and this part OF the lncl-
nation increases during the eclipse, being accu-
rately shown in the small diagrams, figures / to l.


EcLIPTTcAL ORDERS.


The ancient Chaldeans discovered that after
period OF eighteen years and eleven days. or
period OF 223 iunations oclipses return in the
same order. and present very nearly the same ap.
pearance. During that time there are generally
seventy eclpses. twenty-nine OF which are Of the
moon. 0ae-half OF those are invisible. In Gpnss-