However, by dint of a natural phenomenon, identical with that produced on the moon when she is in her octants, the contour of the terrestrial globe could be traced.  Its entire disc appeared slightly visible through an effect of pale light, less appreciable than that of the moon.  The reason of this lessened intensity is easy to understand.  When this reflection is produced on the moon it is caused by the solar rays which the earth reflects upon her satellite.  Here it was caused by the solar rays reflected from the moon upon the earth.  Now terrestrial light is thirteen times more intense than lunar light on account of the difference of volume in the two bodies.  Hence it follows that in the phenomenon of the pale light the dark part of the earth’s disc is less clearly outlined than that of the moon’s disc, because the intensity of the phenomenon is in proportion to the lighting power of the two stars.  It must be added that the terrestrial crescent seems to form a more elongated curve than that of the disc—­a pure effect of irradiation.

Whilst the travellers were trying to pierce the profound darkness of space, a brilliant shower of falling stars shone before their eyes.  Hundreds of meteors, inflamed by contact with the atmosphere, streaked the darkness with luminous trails, and lined the cloudy part of the disc with their fire.  At that epoch the earth was in her perihelion, and the month of December is so propitious to these shooting stars that astronomers have counted as many as 24,000 an hour.  But Michel Ardan, disdaining scientific reasoning, preferred to believe that the earth was saluting with her finest fireworks the departure of her three children.

This was all they saw of the globe lost in the darkness, an inferior star of the solar world, which for the grand planets rises or sets as a simple morning or evening star!  Imperceptible point in space, it was now only a fugitive crescent, this globe where they had left all their affections.

For a long time the three friends, not speaking, yet united in heart, watched while the projectile went on with uniformly decreasing velocity.  Then irresistible sleep took possession of them.  Was it fatigue of body and mind?  Doubtless, for after the excitement of the last hours passed upon earth, reaction must inevitably set in.

“Well,” said Michel, “as we must sleep, let us go to sleep.”

Stretched upon their beds, all three were soon buried in profound slumber.

But they had not been unconscious for more than a quarter of an hour when Barbicane suddenly rose, and, waking his companions, in a loud voice cried—­

“I’ve found it!”

“What have you found?” asked Michel Ardan, jumping out of bed.

“The reason we did not hear the detonation of the Columbiad!”

“Well?” said Nicholl.

“It was because our projectile went quicker than sound.”

CHAPTER III.