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which a prediction of the return had been
confirmed, until the orbit of the small, ill-
defined comet found by Pons in 1819 was
computed by Encke, and found to have a
period of 3ˆa years. It was predicted to re-
turn in 1822, and was recognised by him as
identical with many previous comets. This
comet, called after Encke, has showed in
each of its returns an inexplicable reduction
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