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Page 48
[Footnote *: Lockyer.]
Our opportunities for seeing Saturn vary greatly. As the earth at
one part of its orbit presents its south pole [Page 171] to the sun,
then its equator, then the north pole, so Saturn; and we, in the
direction of the sun, see the south side of the rings inclined at an
angle of 27�; next the edge of the rings, like a fine thread of
light; then the north side at a similar inclination. On February
7th, 1878, Saturn was between Aquarius and Pisces, with the edge of
the ring to the sun. In 1885, the planet being in Taurus, the south
side of the rings will be seen at the greatest advantage. From 1881
till 1885 all circumstances will combine to give most favorable
studies of Saturn. Meanwhile study the picture of it. The outer ring
is narrow, dark, showing hints of another division, sometimes more
evident than at others, as if it were in a state of flux. The inner,
or second, ring is much brighter, especially on the outer edge, and
shading off to the dusky edge next to the planet. There is no sign
of division into a third dusky innermost ring, as was plainly seen
by Bond. This, too, may be in a state of flux.
The markings of the planet are delicate, difficult of detection,
and are not like those stark zebra stripes that are so often
represented.
The distance between the planet and the second ring seems to be
diminished one-half since 1657, and this ring has doubled its breadth
in the same time. Some of this difference may be owing to our greater
telescopic power, enabling us to see the ring closer to the planet;
but in all probability the ring is closing in upon the central
body, and will touch it by A.D. 2150. Thus the whole ring must
ultimately fall upon the planet, instead of making a satellite.
We are anxious to learn the nature of such a ring. [Page 172]
Laplace mathematically demonstrated that it cannot be uniform and
solid, and survive. Professor Peirce showed it could not be fluid,
and continue. Then Professor Maxwell showed that it must be formed
of clouds of satellites too small to be seen individually, and too
near together for the spaces to be discerned, unless, perhaps, we
may except the inner dark ring, where they are not near enough to
make it positively luminous. Indeed, there is some evidence that the
meteoroids are far enough apart to make the ring partially
transparent.
We look forward to the opportunities for observation in 1882 with
the brightest hope that these difficult questions will be solved.
_Satellites of Saturn._
The first discovered satellite of Saturn seen by Huyghens was in
1655, and the last by the Bonds, father and son, of Cambridge,
in 1848. These are eight in number, and are named:
Distant from Saturn's centre.
I. Mimas 119,725 miles.
II. Enceladus 153,630 "
III. Tethys 190,225 "
IV. Dione 243,670 "
V. Rhea 340,320 "
VI. Titan 788,915 "
VII. Hyperion 954,160 "
VIII. Japetus 2,292,790 "
Titan can be seen by almost any telescope; I., II., and III., only
by the most powerful instrument. All except Japetus revolve nearly
in the plane of the ring. Like the moons of Jupiter, they present
remarkable and unaccountable variations of brilliancy. An inspection
[Page 173] of the table reveals either an expectation that another
moon will be discovered between V. and VI., and about three more
between VII. and VIII., or that these gaps may be filled with groups
of invisible asteroids, as the gap between Mars and Jupiter. This
will become more evident by drawing Saturn, the rings, and orbits of
the moons all as circles, on a scale of 10,000 miles to the inch.
Saturn will be in the centre, 70,000 miles in diameter; then a gap,
decreasing twenty-nine miles a year to the first ring, of, say,
10,000 miles; a dark ring 9000 miles wide; next the brightest ring
18,300 miles wide; then a gap of 1750 miles; then the outer ring
10,000 miles wide; then the orbits of the satellites in order.
If the scenery of Jupiter is magnificent, that of Saturn must be
sublime. If one could exist there, he might wander from the illuminated
side of the rings, under their magnificent arches, to the darkened
side, see the swift whirling moons; one of them presenting ten times
the disk of the earth's moon, and so very near as to enable him
to watch the advancing line of light that marks the lunar morning
journeying round that orb.
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