Chapter 6 - Page 2

herself. To such they answered, "Go into your
dining-room, and walk round the table in such a way as to always
keep your face turned toward the center; by the time you will
have achieved one complete round you will have completed one
turn around yourself, since your eye will have traversed
successively every point of the room. Well, then, the room is
the heavens, the table is the earth, and the moon is yourself."
And they would go away delighted.

So, then the moon displays invariably the same face to the
earth; nevertheless, to be quite exact, it is necessary to add
that, in consequence of certain fluctuations of north and south,
and of west and east, termed her libration, she permits rather
more than half, that is to say, five-sevenths, to be seen.

As soon as the ignoramuses came to understand as much as the
director of the observatory himself knew, they began to worry
themselves regarding her revolution round the earth, whereupon
twenty scientific reviews immediately came to the rescue.
They pointed out to them that the firmament, with its infinitude
of stars, may be considered as one vast dial-plate, upon which the
moon travels, indicating the true time to all the inhabitants of
the earth; that it is during this movement that the Queen of
Night exhibits her different phases; that the moon is _full_
when she is in _opposition_ with the sun, that is when the three
bodies are on the same straight line, the earth occupying the
center; that she is _new_ when she is in _conjunction_ with the
sun, that is, when she is between it and the earth; and, lastly
that she is in her _first_ or _last_ quarter, when she makes
with the sun and the earth an angle of which she herself occupies
the apex.

Regarding the altitude which the moon attains above the horizon,
the letter of the Cambridge Observatory had said all that was to
be said in this respect. Every one knew that this altitude
varies according to the latitude of the observer. But the only
zones of the globe in which the moon passes the zenith, that is,
the point directly over the head of the spectator, are of
necessity comprised between the twenty-eighth parallels and
the equator. Hence the importance of the advice to try the
experiment upon some point of that part of the globe, in order
that the projectile might be discharged perpendicularly, and so
the soonest escape the action of gravitation. This was an
essential condition to the success of the enterprise, and
continued actively to engage the public attention.

Regarding the path described by the moon in her revolution round
the earth, the Cambridge Observatory had demonstrated that this
path is a re-entering curve, not a perfect circle, but an
ellipse, of which