Earth; but there is not a constellation that can be recognised, because all the celestial perspectives have changed; stars of the first magnitude have become of the second and of the third; whilst others, of lesser magnitudes, seen nearer, shine with increased brilliancy; and, above all, the respective situation of the stars as regards one another has completely changed in consequence of the different position of that star and of the Earth. QUÆRENS. Therefore the appearance of the constellation which one has so long believed to be ineffaceably traced upon the vaulted sky is only due to perspective. In changing our position we change our perspective, and our sky is no longer the same. But, then, ought we not to have a change of celestial perspective every six months, since during this interval the Earth has greatly altered its position, having removed to a distance of seventy-four millions of leagues from the place it formerly occupied? LUMEN. This objection proves that you have perfectly comprehended the principle of the deformation of the constellations as one moves in any direction in space. It would be, as you suppose, if the Earth's orbit were of a dimension sufficiently vast for the two opposite points of this orbit to change the view of this celestial scenery. QUÆRENS. Seventy-four millions of leagues-- LUMEN. Are as nothing in the order of celestial distances, and can no more affect the perspectives of the stars, than taking a step in the cupola of the Pantheon would change the apparent position of the buildings in Paris to the eye of the observer. [Sidenote: The charts of the Middle Ages.] QUÆRENS. Certain charts of the Middle Ages represent the Zodiac as an arch in the heavens, and place some of the constellations, such as Andromeda, the Lyre, Cassiopea, and the Eagle, in the same region as the Seraphim, the Cherubim, and the Thrones. That, therefore, was simply fancy, since constellations have no real existence, but are simply appearances due to perspective. LUMEN. Certainly the old heaven of theology has no legitimate place to-day, and simple common sense shows that it does not exist. Two truths cannot oppose one another; it is a necessity that the spiritual heaven should accord with the physical heaven, and the object of my various conversations is the demonstration of this truth. Upon the world of Andromeda of which I speak, there is nothing resembling the constellation of Andromeda. Seen from the Earth, those stars which appear joined and have served on the celestial landscape to distinguish the daughter of Cepheus and Cassiopea, are in reality spread out in space at all sorts of distances, and in every direction. One cannot find either there or elsewhere the least vestige of the tracings of terrestrial mythology. [Sidenote: The poetry of the heavens lost.]