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and we find that though we cannot see the satellites separate, their different speeds declare themselves in the spectroscope, just as Clerk Maxwell said (see p. 275). One more point about the ring: it does not always appear to us in the same aspect; sometimes it is open and sometimes it closes up until we see it edgeways, and then it disappears altogether. This shows how very thin it must be, and we can infer that the little satellites composing it must be very small indeed. You might say they need only be very flat; but it is hardly likely that they would keep their flatness always in the plane of the ring when they are jostling round at different rates. It seems most reasonable to think that they are small in all ways.

Now please look at this diagram showing the distances of the planets from the Sun. We can only imitate them on a very small scale, of course. You remember that our Earth is about 93 million miles from the Sun; let us call this 10 inches or 10 millimetres or whatever we like. Then the other distances can be written down as follows

  Bode's Law   Distance
Mercury 4 + 0 = 4
Venus 4 + 3 = 7
Earth 4 + 6 = 10
Mars 4 + 12 = 16
(Minor Planets) 4 + 24 = (28)
Jupiter 4 + 48 = 52
Saturn 4 + 96 = 100
Uranus 4 + 192 = 196
Neptune 4 + 384 = 388