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POPULAR SCIENCE REVIEW. 
or the rings of Saturn, which each in their day impressed men 
with new ideas of the celestial mechanism. But the truth 
could not long he delayed. The new body being watched, 
and its orbit rigorously computed from a series of observed 
positions, revealed its true character, and Herschel was awarded 
the honour due to the author of a discovery of such importance. 
His diligence and pertinacity alone had enabled him to search 
out from amongst the multitude of stars thickly strewn over the 
firmament, this unknown and well-nigh invisible planet, which 
during all the preceding years of the world’s history had eluded 
human perception. Men had been all unconscious of its exist- 
ence, as it had been slowly completing its circuits around the 
Sun, obedient to the same laws as the other planets of the solar 
system, and awaiting the hour when the unfailing eye of 
Herschel should introduce it as the faint and far-off planet 
girding our system within its expansive folds. 
As soon as the existence of the new orb was confirmed, and 
the fact rendered indisputable, the question naturally arose 
whether it had ever been seen in former years by the authors 
of star-catalogues, who could hardly have overlooked an object 
like this, though its planetary nature had manifestly escaped 
detection. It was just perceptible to the naked eye, shining 
like a star of the sixth magnitude, and ought to have been dis- 
tinguished by those who had reviewed the heavens with the 
purpose of determining and mapping the positions of the stars. 
Reference was therefore made to the chief catalogues, when it 
was found at once that the planet had been unquestionably 
observed by Tobias Mayer, Le Monnier, Bradley, and Flamsteed. . 
It was several times noted by these observers: by Le Monnier no 
less than twelve times, and by Flamsteed on six occasions ; and 
it is remarkable that in every instance its true character escaped 
detection. Neither its special appearance nor its motion attracted 
attention, so that it was merely catalogued as an ordinary fixed 
star. Thus Herschel was not anticipated in his discovery. It 
remained for him, in 1781, to note its exceptional aspect, and to 
specify it as an object requiring critical investigation. But 
the early observations above alluded to served a useful purpose 
in testing the accuracy of the computed orbit, for without waiting 
many years to compare the theoretical and observed positions, 
astronomers had, in these old records, a reliable series of points, 
through which the previous course of the planet could be traced. 
The calculations showed that its mean distance from the | 
sun was some 1,750,000,000 miles, and that a revolution was 
completed in about eighty-four years. It was also found to be i 
a very large planet, greatly exceeding either Mercury , Venus , 
the Earth , or Mars , though considerably inferior to either 
J upiter or Saturn. 
