[Illustration: IV]
IV.--If the comet have satellites, we shall see, according to the
relative position of these, several tails appear, and these will seem to
form at different epochs. If c and s be the positions of a comet and a
satellite, it will be seen that if, while the comet is proceeding to c',
the satellite, through its revolution around it, goes to s', the traces
formed at c and s will be extended to d and d', and that we shall have
two tails, c' d and s' d', which will be separated at d and d' and seem
to be confounded toward c' s'.
V.--When the comet recedes from the sun, the same effect will occur--the
tail will precede it, and will be so much the more in a line with the
sun in proportion as the velocity of the solar waves exceeds that of the
comet.
If we draw a complete diagram (Fig. 4), and admit that the alteration of
the solar waves persists indefinitely, we shall see (supposing the
phenomenon to begin at a) that when the comet is at a 1, the tail will
and be at a 1 b; when it is a 2 the tail will be at a 2 b'; and when it
is at a 4, the tail will have become an immense spiral, a 4 b'''. As in
reality the trace is extinguished in space, we never see but the origin
of it, which is the part of it that is constantly new--that is to say,
the part represented in the spirals of Fig.
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