THE LOST COMET AND ITS METEOK-TRAIN. 
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Those particular meteors which were travelling twelve weeks 
behind the head of the comet, although, speaking generally, 
they would follow the comet’s track, would nevertheless not be 
found travelling in precisely the same orbit, nor would they 
cross the earth’s orbit precisely where the comet’s orbit did at 
the time. For they would have been subjected to perturbations 
differing notably in character from those which had affected the 
comet itself. It must be remembered that the circumstances 
which separated such meteors by so great a distance from the 
head have not taken place in a few years, in a few revolutions 
of the comet, or even in a few centuries. But even if we take 
only the last half century or so, and consider the history of those 
meteors during that time, it will be manifest that their per- 
turbations have differed considerably from those which have 
affected their leader, so to term the comet in whose track they 
follow. In the course of those years the comet has made seven 
or eight revolutions, and so have the meteors, while Jupiter, 
the chief disturber of Biela’s comet, has made four or five revolu- 
tions. In the course of this period the comet must have been 
more than once so placed as to be very considerably disturbed 
by Jupiter, because as a matter of fact the path of the comet 
passes not very far (near its aphelion) from the path of Jupiter. 
The same general statement is true, of course, of the meteors 
twelve weeks behind. Now, whenever it happened that the 
comet was at its nearest to Jupiter, when passing that critical 
portion of its orbit, the meteors twelve weeks behind were 
either not brought so fully under the influence of Jupiter’s 
attraction, or if they were, they were perturbed by him in a 
different manner. This is manifest if we consider how enor- 
mous is the real distance corresponding to the twelve weeks or 
so by which the meteors are behind the comet. And again, 
when the meteors chanced to be at their nearest to Jupiter 
when passing the critical part of their orbit, the comet, twelve 
weeks in front, was either not brought so fully under Jupiter’s 
influence, or was perturbed in a different way. 
Now whenever a perturbation has been produced, it affects 
the orbit of the perturbed body. Supposing the comet and 
meteors moving in precisely the same orbit at a particular 
moment, when Jupiter is pulling the comet in a certain way 
and the meteors in a different way, then forthwith the comet 
and meteors travel in different orbits. The difference may be 
slight, close by the place where such perturbations are produced, 
but it may nevertheless appreciably affect the positions which 
will be occupied by the comet and meteors when severally 
traversing some other and distant part of their orbit (as for 
instance when they are at their descending node close by the 
earth’s track). And again, although in the long run there are 
