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period of rotation to be 24h. 37m. 22s.,62–
or one-tenth of a second less than the period
deduced by R. A. Proctor from a drawing
by Hooke in 1666.
It must be noted that, if the periods
of rotation both of Mercury and Venus be
about twenty-four hours, as seems proba-
ble, all the four planets nearest to the sun
rotate in the same period, while the great
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