THE MAJOR PLANETS. 



217 



thousand miles. More recent observations made by Sir William Herschcl 

 establish the fact that this ring is not, as was first supposed, a single anmilnr 

 plate of matter, but has a division by which it is separated into two indepen- 

 dent rings, one outside the other, which have no mutual point of contact or 

 connexion. This separation appeared at first, as a dark streak upon tin: surface 

 of the ring running parallel to its edges. Sir William Herschcl, however, 

 succeeded in seeing stars which were behind the ring through this apparent 

 streak, and consequently arrived at the conclusion that it was an opening r 

 separation between two independent rings. It was found also that trie sur- 

 face of the ring was marked by parallel streaks or bands, like the bens of the 

 planet. 



Very recent, observations made at Rome upon this planet, appear 10 counten- 

 ance the supposition that the ring, instead of being double, is qtum.iple, and 

 that there are four divisions instead of one, as supposed by Sir Winiam Her- 

 schel. It is even said that six divisions have been observed, and therefore 

 'there are seven independent rings, one within another, all being concentric 

 with the planet and in the plane of its equator. 



One of the most striking discoveries of Sir William Herscuel respecting 

 Saturn, was the revolution of the rings around the planet. He found that they 

 revolve round their own centre and that of the planet in their own plane, and 

 that they complete a revolution in the same time that a satellite would revolve- 

 in, at the same distance. Their motion, therefore, is conformable to the laws 

 of gravitation which would govern that of satellites or moons. Tne dimension!? 

 of the rings, as observed by Sir William Herschel, are as follows : 



Miles. 



Exterior diameter of exterior ring 176,418 



Interior diameter of exterior ring 155,272 



Breadth of exterior ring . . 10,573 



Exterior diameter of interior ring 151,690 



Interior diameter of interior ring 1 17,339 



Breadth of the interior ring 17,175 



Equatorial diameter of the planet 79, 1 60 



Interval between the planet and the interior ring 19,090 



Interval of the rings 1,791 



Thickness of the rings not exceeding 100 



It appears then that the thickness of the rings is incomparably smaller than 

 thcirbreadth ; the thickness being not more than the three hundredth part of 

 the breadth. 



One of the circumstances attending the contemplation of the planet Saturn 

 which excites most surprise, is the fact that the planet and the two rings should 

 be capable of maintaining their relative position with the prodigious velocity 

 with which they move round the sun, without either overtaking the other or 

 any collision taking place. Let it be remembered that the circumference of 

 Saturn's orbit round the sun measures about six thousand millions of miles, and 

 that the planet completes this circuit in less than thirty years, so that he moves 

 at the rate of about seven millions and three quarter miles per day, or three 

 hundred and twenty-five thousand miles an hour. This is a velocity six hun- 

 dred ;md fifty times greater than that of a cannon-ball. Yet with this prodigious 

 celerity of motion continued for countless ages, neither of the rings has ever 

 overtaken the planet or the planet overtaken them, and still more wonderful, 

 the two rings, separated only by a space of about eighteen hundred miles, 

 which they would move over with their orbitual motion in about three minutes, 

 have never overtaken each other. This astonishing precision of movement 

 would become still more surprising if it be true, as' it is suspected to be, that 

 there are five or more independent rings, one included within the other. 



