iptic. It hence follows that Uranus is at all times only to be met
with along the ecliptic, and it is possible to calculate where the
planet has been in each year. It was thus seen that in 1690 the planet
was situated in that part of the ecliptic where Flamsteed was at the
same date making his observations. It was natural to search the
observations of Flamsteed, and see whether any of the so-called stars
could have been Uranus. An object was found in the "Historia
Coelestis" which occupied a position identical with that which Uranus
must have filled on the same date. Could this be Uranus? A decisive test
was at once available. The telescope was directed to the spot in the
heavens where Flamsteed saw a sixth-magnitude star. If that were really
a star, then would it still be visible. The trial was made: no such star
could be found, and hence the presumption that this was really Uranus
could hardly be for a moment doubted. Speedily other confirmation flowed
in. It was shown that Uranus had been observed by Bradley and by Tobias
Mayer, and it also became apparent that Flamsteed had observed Uranus
not only once, but that he had actually measured its place four times in
the years 1712 and 1715. Yet Flamsteed was never conscious of the
discovery that lay so nearly in his grasp. He was, of course, under the
impression that all these observations related to different stars. A
still more remarkable case is that of Lemonnier, who had actually
observed Uranus twelve times, and even recorded it on four consecutive
days in January, 1769. If Lemonnier had only carefully looked over his
own work; if he had perceived, as he might have done, how the star he
observed yesterday was gone to-day, while the star visible to-day had
moved away by to-morrow, there is no doubt that Uranus would have been
discovered, and William Herschel would have been anticipated. Would
Lemonnier have made as good use of his fame as Herschel did? This seems
a question which can never be decided, but those who estimate Herschel
as the present writer thinks he ought to be estimated, will probably
agree in thinking that it was most fortunate for science that Lemonnier
did _not_ compare his observations.[31]

These early accidental observations of Uranus are not merely to be
regarded as matters of historical interest or curiosity. That they are
of the deepest importance with regard to the science itself a few words
will enable us to show. It is to be remembered that