The philosophers who teach that the universe is both infinite and homogeneous resemble microbes who think that their cell is the universe. Let us imagine the microbes in a particle of rust attempting to reason on the life of iron according to their own observations. For them, the world is a bit of iron attacked by oxygen. There is nothing else in nature. All their science leads them to conclude that the universe is made of iron. If they could have any vague notion about the existence of grass, insects, men, the sun, Jupiter or Sirius, they would be firmly convinced that they were all made of iron. If, in their particle of rust, they had observed the movements of translation and rotation in the constituent atoms of iron and could have risen to astronomical notions beyond their sphere, they would conclude that the other planetary systems are also made of iron and that none but iron-dwellers can exist. If we suppose that not only our own solar system but our visible universe and the other universes which succeed each other without end in the depths of infinite space are all constructed on the same zoological plan, we reason like these microbes. Since the publication, a long time ago (1862), of my first work, entitled _The Plurality of Inhabited Worlds_, in which I expounded and discussed the conditions of habitability of the planets of our system as known, to science at the time of publication, several astronomers and philosophers have taken up the same question of the different aspects. Among these studies there is one which seems particularly worthy of attention, recently written by Professor Scheiner, Director of the Potsdam Observatory. I here offer my readers a condensed translation, asking them to excuse the Germanisms which render the style a little rough. But however bitter the rind, the fruit is good. GENERAL REMARKS “The aspect of the starry heavens during a clear and calm night gives a joy which only superior souls can feel. In the bosom of the general silence of nature and in the calm of all our senses our immortal soul whispers an undefinable language and forms conceptions which are difficult to express. If among the thinking beings of our planet there are vulgar spirits which remain slaves to vanity, this globe is to be pitied for having given birth to such creatures, but its value is enhanced by bearing on its surface intelligences capable of rising to the highest contemplations of the spectacle of nature.”