encounter a most vivid brilliancy, which almost pricks the eye with the rapid sparkling of its rays, of such intensity that, in comparison with it, the planets, even Jupiter, and Venus too, are as thoroughly outshone as common and bad glass compared with a highly polished and most sparkling diamond. And although the orb of the Dog-Star appears no larger than the fiftieth part of Jupiter’s disc, nevertheless its brilliancy is great and very strong; so that the form of its disc, which you expect to see, hides itself among the rays of its own refulgence, envelops itself in them, and almost disappears; and it is not distinguished without some difficulty from the rays which surround it. Whereas Jupiter, and still more Saturn, are seen well defined; and their light is without intensity, and, if I may say so, quiescent. Wherefore I think that we shall rightly apply our philosophy if we refer the cause of the twinkling of the fixed stars to vibrations of a brilliancy, which is their own, belonging to their constitution, and inherent in their substance, and say, on the other hand, that the illumination of the planets, which is derived from the sun, and distributed to the world, is limited to their surface.” These are the scientific conclusions in Galileo’s letter; the rest I omit. [30] Proctor (_Other Worlds than Ours_, 1875) has given some reasons for believing that Jupiter and Saturn shine in part with their own light, owing to their great internal heat. You see then, studious reader, how the subtle mind of Galileo, in my opinion the first philosopher of the day, uses this telescope of ours like a sort of ladder, scales the furthest and loftiest walls of the visible world, surveys all things with his own eyes, and, from the position he has gained, darts the glances of his most acute intellect upon these petty abodes of ours—the planetary spheres I mean,—and compares with keenest reasoning the distant with the near, the lofty with the deep. VALE ET DEUM IN OPERIBUS SUIS CELEBRARE NUNQUAM DESINE. KEPLER, _Narratio_. Edinburgh University Press: THOMAS AND ARCHIBALD CONSTABLE, PRINTERS TO HER MAJESTY. End of the Project Gutenberg EBook of The Sidereal Messenger of Galileo Galilei, by Galileo Galilei and Johannes Kepler