“Only I must tell you, my worthy friend, that we are none the less lost men on that account!”

“No, but in another and much pleasanter way!” answered the careless Frenchman, with his most amiable smile.

President Barbicane was right.  By describing this elliptical orbit the projectile was going to gravitate eternally round the moon like a sub-satellite.  It was a new star added to the solar world, a microcosm peopled by three inhabitants, whom want of air would kill before long.  Barbicane, therefore, could not rejoice at the position imposed on the bullet by the double influence of the centripetal and centrifugal forces.  His companions and he were again going to see the visible face of the disc.  Perhaps their existence would last long enough for them to perceive for the last time the full earth superbly lighted up by the rays of the sun!  Perhaps they might throw a last adieu to the globe they were never more to see again!  Then their projectile would be nothing but an extinct mass, dead like those inert asteroids which circulate in the ether.  A single consolation remained to them:  it was that of seeing the darkness and returning to light, it was that of again entering the zones bathed by solar irradiation!

In the meantime the mountains recognised by Barbicane stood out more and more from the dark mass.  They were Mounts Doerfel and Leibnitz, which stand on the southern circumpolar region of the moon.

All the mountains of the visible hemisphere have been measured with perfect exactitude.  This perfection will, no doubt, seem astonishing, and yet the hypsometric methods are rigorous.  The altitude of the lunar mountains may be no less exactly determined than that of the mountains of the earth.

The method generally employed is that of measuring the shadow thrown by the mountains, whilst taking into account the altitude of the sun at the moment of observation.  This method also allows the calculating of the depth of craters and cavities on the moon.  Galileo used it, and since Messrs. Boeer and Moedler have employed it with the greatest success.

Another method, called the tangent radii, may also be used for measuring lunar reliefs.  It is applied at the moment when the mountains form luminous points on the line of separation between light and darkness which shine on the dark part of the disc.  These luminous points are produced by the solar rays above those which determine the limit of the phase.  Therefore the measure of the dark interval which the luminous point and the luminous part of the phase leave between them gives exactly the height of the point.  But it will be seen that this method can only be applied to the mountains near the line of separation of darkness and light.

A third method consists in measuring the profile of the lunar mountains outlined on the background by means of a micrometer; but it is only applicable to the heights near the border of the orb.