if produced, would pass to the left of the sun, as seen from the earth:
the force of the radial stream, however, will not allow this lagging of
the tail, and it is straightened out by this force; but, being directed
to the axis of the vortex, and not to the sun, it is not really in the
plane of the orbit, but is seen in the direction of the upper tail
depicted in the diagram at 3, and, if produced, would pass to the right
of the sun, as seen from T. Now, there is an intermediate position of
the tail, in which it will appear in the prolongation of the radius
vector SC; this position is represented by the middle or central tail of
the comet at 2, yet this is not in the plane of the orbit, it only
appears to be, as may be readily understood by remembering that the
earth at this time is under this plane, and the comet is seen at a
considerable elevation above the plane of the ecliptic. When the comet's
tail becomes directed to the axis of the vortex, or in the _apparent_
position of No. 3, the comet, rapidly careering on its way to the sun,
again leaves the tail behind, and again it is strengthened out by the
radial stream oscillating about the mean position at 2, as observed by
Bessel. From this, it appears, that there is no necessity to make
confusion worse confounded, by resorting to polar forces, which are
about as intelligible as the foundations of the pillars of Atlas.

[Illustration: Fig. 25]

It may be objected that the continued action of the radial stream with
that velocity we have contended for, ought to keep the tail invariably
directed from the axis of the vortex; but, where there are two forces or
tendencies, as in this case, analogy would teach us that a certain
degree of oscillation is a necessary result. There may, also, be slight
and transient changes in the direction of the radial stream. In the
hurricane there are short and fitful blasts inclined to the general
direction of the wind, which must arise from the inertia of the moving
mass of atmosphere, causing temporary condensations and rarefactions. Be
this as it may, we have assigned a cause which satisfies the phenomenon,
without coming into collision with a single principle of celestial
mechanics.

Prof. Struve compared the tail of this comet to a flame, or "ray of fire
shot out from the nucleus, as from some engine of artillery, and driven
on one side by the wind." At the same time, he saw a second emanation
nearly in the opposite direction. This l