I am glad, said the Marchioness, you have given me this genealogy of the sciences; astronomy is the only one that will suit me: geometry, according to your account of it, requires a more selfish heart than mine; and I have not susceptibility enough to attempt poetry with success; I have, however, as much leisure as can be needful for the study of astronomy; it is another favourable circumstance that we are in the country, leading a pastoral life. Do not mistake madam, answered I, talking of planets and fixed stars is not all that constitutes a pastoral life. Was the conversation of the shepherds, in the golden age, confined to astronomy? Ah, said she, but it would be dangerous to conform one's mode of life to their's. No, that of the other shepherds you mention appears preferable to me; therefore let us converse, if you please, in the Chaldean style. After this disposition of the stars was remarked, what followed? The next thing, I replied, was to imagine the arrangement of the different parts of the universe; that is what the learned call making a system. But before I explain to you the first of these systems, give me leave to premise that we are all naturally disposed to the same sort of madness as a certain Athenian of whom you have heard, who had taken it in his head that every vessel which went into the port of Pyreum belonged to him. We chuse to believe that every thing in creation is destined to our service; and when we enquire of some philosophers the use of such a prodigious number of fixed stars, of which a smaller proportion would have been sufficient for all the offices they appear to perform; they coolly answer, they were made to gratify our sight. On this selfish principle it was for a long time supposed that the earth was motionless in the midst of the universe, whilst all the heavenly bodies were created for the sole purpose of journeying round, and distributing their light to her. Next to the earth they placed the moon, after the moon, Mercury, then Venus, the Sun, Mars, Jupiter, Saturn; beyond all these the firmament of fixed stars. It was imagined that the earth was stationed exactly in the middle of the circles described by these planets which extended in proportion to their distance from the earth, and that consequently the most remote planets required a longer time to perform their revolutions, which certainly is true. But, interrupted the Marchioness, I can't see why you should disapprove such an arrangement of the universe, it appears to me sufficiently commodious and intelligible, I really feel quite satisfied with it. I have taken pains, answered I, to represent this system in the most favourable point of view; if I were to explain it exactly as it was conceived by Ptolemy the author of it, and his disciples, you would be quite shocked. As the motions of the planets are irregular, being sometimes quicker, sometimes slower; going sometimes in one direction, sometimes in another; now nearer to