252 



THE MAJOR PLANETS. 



hundred and eighty of Saturn's days. Such are the seven different months 

 prevalent upon SATURN. 



The magnitudes of the satellites of Saturn have not been certainly ascer- 

 tained ; their distances from the earth are too great to enable us hitherto, ac- 

 tually to measure their diameters. 



Sir John Herschel estimates the diameter of the most remote satellite to be 

 little less than that of Mars, which is 4,200 miles. The next to it cannot be 

 much less, being the most conspicuous in its appearance. As to the magni- 

 tudes of the four minor satellites, we are left to conjecture. 



It is usual to designate these bodies in the order of their discovery, and not 

 in the order of their distances from Saturn. If the following figures represent 

 the succession of their distances, the order of their discovery is that expressed 

 above the figures respectively : 



Seventh, Sixth, First, Second, Third, Fourth, Fifth. 

 1 234567 



The distance of the nearest satellite from the surface of Saturn does not ex- 

 ceed 80,000 miles, a space equal to one diameter of the planet. Its distance 

 beyond the edge of the ring is only 18,000 miles. 



This moon completes its revolution round Saturn in 22^ hours, or a little 

 more than two Saturniah days. In one of the planet's days it passes therefore 

 from new to full moon, and in the next from full to new moon. Its change of 

 phase from hour to hour must, be distinctly perceivable. 



It is probable, from analogy, that its magnitude is greater than that of our 

 moon, and since its distance from the surface of Saturn is three times less than 

 that, of our moon, its apparent diameter at Saturn must be more than three 

 times greater. It will therefore appear with a disk at least ten times as great 

 as that of our moon. 



The next moon is at a distance of 160,000 miles from the centre, and 120,000 

 miles from the surface of Saturn, which being half the distance of our moon 

 from the earth, shows that if, as is probable, this satellite be equal in magnitude 

 to our moon, it will appear with a disk four times as great. It completes its 

 revolution in three of Saturn's days, within which time it exhibits all its phases. 



The moon next in order is at a distance of 200,000 miles from the centre 

 and 160,000 from the surface of the planet. It appears a little less than four 

 times larger than our moon and goes through all its phases in less than five 

 of Saturn's days. 



The next satellite is at a distance of 260,000 miles from the centre and 

 220,000 miles from the surface of Saturn, and therefore appears larger at Sat- 

 urn than our moon does at the earth. It passes through all its phases in six 

 and a half of Saturn's days. 



Thus' it appears that Saturn is supplied with four moons, all moving nearer 

 to his surface than ours is to the earth, and appearing from twice to ten times as 

 large, and passing through all their phases in from two to seven of Saturn's days. 



The fifth moon from Saturn, completing its month in eleven and a half of 

 Saturn's days, is at a distance a little greater than that of our moon, and prob- 

 ably appears of the same magnitude seen from Saturn. The sixth moon, com- 

 pleting its month in forty of Saturn's days, is at more than three times the dis- 

 tance of our moon, but is twice its diameter. It appears from Saturn but little 

 less than ours. The most remote of this system of moons completes its rev- 

 olution in two hundred Satumian days, and its distance from Saturn is ten 

 times that of our moon from the earth. This is the largest moon of the sys- 

 tem, but still, owing to its great distance, must appear smaller at Saturn than 

 ours does at the earth. 



