"Well done!" exclaimed Barbicane. "Do you know, Michel, for an artist you are intelligent."
"Yes," answered Michel carelessly, "we are all intelligent on the
Boulevard des Italiens."
Barbicane shook hands gravely with his amiable companion, and went on enumerating the few advantages reserved to the inhabitants of the visible face.
Amongst others he quoted the observations of the sun's eclipses, which can only be seen from one side of the lunar disc, because the moon must be in opposition before they can take place. These eclipses, caused by the interposition of the earth between the sun and the moon, may last two hours, during which, on account of the rays refracted by its atmosphere, the terrestrial globe can only appear like a black spot upon the sun.
"Then," said Nicholl, "the invisible hemisphere is very ill-treated by
Nature."
"Yes," answered Barbicane, "but not the whole of it. By a certain movement of liberation, a sort of balancing on its centre, the moon presents more than the half of her disc to the earth. She is like a pendulum, the centre of gravity of which is towards the terrestrial globe, and which oscillates regularly. Whence comes that oscillation? Because her movement of rotation on her axis is animated with uniform velocity, whilst her movement of translation, following an elliptical orb round the earth, is not. At the perigee the velocity of translation is greater, and the moon shows a certain portion of her western border. At her apogee the velocity of rotation is greater, and a morsel of her eastern border appears. It is a strip of about eight degrees, which appears sometimes on the west, sometimes on the east. The result is, therefore, that of a thousand parts the moon shows five hundred and sixty-nine."
"No matter," answered Michel; "if we ever become Selenites, we will inhabit the visible face. I like light."
"Unless," replied Nicholl, "the atmosphere should be condensed on the other side, as certain astronomers pretend."
"That is a consideration," answered Michel simply.
In the meantime breakfast was concluded, and the observers resumed their posts. They tried to see through the dark port-light by putting out all light in the projectile. But not one luminous atom penetrated the obscurity.