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an inspiration for the mathematical astronomer.
Clairaut, assisted by Lalande, found that
Saturn would retard the comet 100 days,
Jupiter 518 days, and predicted its return
to perihelion on April 13th, 1759. In his
communication to the French Academy, he
said that a comet travelling into such dis-
tant regions might be exposed to the influ-
ence of forces totally unknown, and ”even
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