the telescope lest he should see them and be convinced. He died shortly afterwards. 'I hope,' said the caustic Galileo, 'that he saw them while on his way to heaven'"[24] CHAPTER XIII. SATURN. The Position of Saturn in the System--Saturn one of the Three most Interesting Objects in the Heavens--Compared with Jupiter--Saturn to the Unaided Eye--Statistics relating to the Planet--Density of Saturn--Lighter than Water--The Researches of Galileo--What he found in Saturn--A Mysterious Object--The Discoveries made by Huyghens half a Century later--How the Existence of the Ring was Demonstrated--Invisibility of the Rings every Fifteen Years--The Rotation of the Planet--The Celebrated Cypher--The Explanation--Drawing of Saturn--The Dark Line--W. Herschel's Researches--Is the Division in the Ring really a Separation?--Possibility of Deciding the Question--The Ring in a Critical Position--Are there other Divisions in the Ring?--The Dusky Ring--Physical Nature of Saturn's Rings--Can they be Solid?--Can they even be Slender Rings?--A Fluid?--True Nature of the Rings--A Multitude of Small Satellites--Analogy of the Rings of Saturn to the Group of Minor Planets--Problems Suggested by Saturn--The Group of Satellites to Saturn--The Discoveries of Additional Satellites--The Orbit of Saturn not the Frontier of our System. At a profound distance in space, which, on an average, is 886,000,000 miles, the planet Saturn performs its mighty revolution around the sun in a period of twenty-nine and a half years. This gigantic orbit formed the boundary to the planetary system, so far as it was known to the ancients. Although Saturn is not so great a body as Jupiter, yet it vastly exceeds the earth in bulk and in mass, and is, indeed, much greater than any one of the planets, Jupiter alone excepted. But while Saturn must yield the palm to Jupiter so far as mere dimensions are concerned, yet it will be generally admitted that even Jupiter, with all the retinue by which he is attended, cannot compete in beauty with the marvellous system of Saturn. To the present writer it has always seemed that Saturn is one of the three most interesting celestial objects visible to observers in northern latitudes. The other two will occupy our attention in future chapters. They are the great nebula in Orion, and the star cluster in Hercules.