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times that of the Earth; period of revolution, 217.387 years; mean long.,
Jan. 1st, 1847, 318 degrees 47'; mass, 1/9300th; heliocentric long., Jan
1st1847, 326 degrees 32'. Essential difficulties still intervened, however,
and as the remoteness of the planet rendered it improbable that its disk
would be discernible by any telescopic instrument, no other means remained
for detecting the suspected body but its planetary motion, which could only
be ascertained by mapping, after every observation, the quarter of the
heavens scanned, and by a comparison of the various maps. Fortunately for
the verification of Leverrier's predictions, Dr. Bremiker had just completed
a map of the precise region in which it was expected the new planet would
apper, this being one of a series of maps made for the Academy of Berlin, of
the small stars along the entire zodiac. By means of this valuable
assistance, Dr. Galle, of the Berlin Observatory, was led, on the 25th of
September, 1846, by the discovery of a star of the eighth magnitude, not
recorded in Dr. Bremiker's map, to make the first observation of the planet
predicted by Leverrier. By a singular coincidence, Mr. Adams, of Cambridge,
had predicted the appearance of the planet simultaneously with M.
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