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ied by a year and a-half, and the inclination
of the orbit to the ecliptic diminished with
successive apparitions. But he knew from
previous calculations that this might eas-
ily be due to planetary perturbations. Fi-
nally, he arrived at the conclusion that all
of these comets were identical, travelling in
an ellipse so elongated that the part where
the comet was seen seemed to be part of
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