the great festivals by similar illuminations which would sometimes follow close upon one another. The fires would serve another purpose, inasmuch as they would thin out the forests and provide fresh arable ground for an increasing population. Large migrations of people would be prevented, and the consequent wars would be avoided and the race would remain united.” One must acknowledge that these ideas of Gruithuisen are most fantastic. I have frequently observed this unilluminated hemisphere of Venus, notably in September 1895 and in April 1897: it appeared to me of a violet colour, and the idea of illuminations by the inhabitants is pure romance. He also then passes in review the ideas of Kant which one finds expounded in the two works cited above and which therefore I need not quote. We know that for the Philosopher of Königsberg the intelligence and the degree of perfection of the inhabitants of the planets is in proportion to their distance from the sun. We may add to the remarks of M. Scheiner that the writers who have dealt with the question of the plurality of worlds have nearly all judged the planets from the appearances they present to us from our point of observation, and have assumed the harmony of nature according to the manner of Bernardin de St. Pierre. For this occasion I have re-read his hook with some interest. To this very simple member of the Institut, Venus is a bright world peopled by amorous natives “who give themselves up to dance, festivals, and songs, or compete for swimming prizes, like the happy islands of Tahiti”; the inhabitants of Mars are warlike, “resembling the northern Germans, their forests and hills, their atmosphere resounding to the warlike sound of their horns and that of drums and trumpets which announce the spilling of blood”; on Jupiter “they resemble the Dutch, being industrious, patient, wise, reflective, and tending their numerous herds in their vast fields,” etc., etc. The author of _Paul et Virginie_ remains purely terrestrial in these descriptions, which he believes to be astronomical. But let us return to the dissertation of M. Scheiner. He passes on to the purely scientific aspect of the question, which is the only one which interests us here. THE ORIGIN OF LIFE The problem of knowing if worlds other than the Earth, being habitable, are really inhabited, depends really upon this question: How did life appear on this Earth?