"In reply to another question which I asked, my interlocutor added: 'As long as the south pole of Uranus was turned toward the earth, in relation to a terrestrial observer, the satellites seemed to move from left to right, and it was erroneously concluded from this that they were going from east to west: this state of things lasted for about forty-two years. When the north pole of Uranus is turned toward the earth, his satellites run their course from right to left, but, in either case, always from the west to the east.' "I thereupon asked him how it happened that the error had not been detected forty-two years after William Herschel's discovery of Uranus. He replied, 'It is because people repeat that which the authorities who have preceded them have said. Dazzled by the results obtained by their predecessors, they do not take the trouble to think.'" Such is the "revelation" of a spirit on the system of Uranus, published by Drayson and presented by Aksakof and other authors as an undeniable proof of the intervention of a spirit in the solution of this problem. The following is the result of an impartial discussion of this very interesting subject. The reasoning of the "spirit" is false. The system of Uranus is almost perpendicular to the plane of its orbit. It is the direct opposite of that of the satellites of Jupiter, which turn almost in the plane of their orbit. The inclination of the plane of the satellites to the ecliptic is 98 deg., and the planet ascends almost in the plane of the ecliptic. This is a fundamental consideration in the picture which we ought to make to ourselves of the aspect of this system seen from the earth. Let us, however, adopt for the method of movement of these satellites around their planet the projection upon the plane of the ecliptic, as has always been the custom. The author maintains that, "when the north pole of Uranus is turned toward the earth, his satellites run their course from right to left, that is to say from west to east"; he indorses the communication of the spirit to the effect that the astronomers are in error and that the satellites of Uranus really revolve around their planet from west to east, in the same way that the moon revolves around the earth. In order to give ourselves an exact account of the position and of the method of the movements of this system, let us construct a special geometrical figure, clear and precise. Let us represent upon a plane the appearance of the orbit of Uranus and of its satellites seen from the northern hemisphere of the celestial sphere (Fig. A). The part of the orbit of the satellites above the plane of the orbit of Uranus has been drawn with heavy lines and hatching, the lower part in dotted lines only.