natural order in which the human mind proceeds in the acquisition
of astronomical knowledge is minute and accurate observation of the
phenomena of the heavens, the skillful discussion and analysis of these
observations, and sound philosophy in generalizing the results.

In pursuing this course, however, a difficulty presented itself, which
for ages proved insuperable--and which to the same extent has existed
in no other science, viz.: that all the leading phenomena are in their
appearance delusive. It is indeed true that in all sciences superficial
observation can only lead, except by chance, to superficial knowledge;
but I know of no branch in which, to the same degree as in astronomy,
the great leading phenomena are the reverse of true; while they yet
appeal so strongly to the senses, that men who could foretell eclipses,
and who discovered the precession of the equinoxes, still believed that
the earth was at rest in the center of the universe, and that all the
host of heaven performed a daily revolution about it as a center.

It usually happens in scientific progress, that when a great fact is at
length discovered, it approves itself at once to all competent judges.
It furnishes a solution to so many problems, and harmonizes with so many
other facts,--that all the other _data_ as it were crystallize at once
about it. In modern times, we have often witnessed such an impatience,
so to say, of great truths, to be discovered, that it has frequently
happened that they have been found out simultaneously by more than one
individual; and a disputed question of priority is an event of very
common occurrence. Not so with the true theory of the heavens. So
complete is the deception practiced on the senses, that it failed more
than once to yield to the suggestion of the truth; and it was only when
the visual organs were armed with an almost preternatural instrumental
power, that the great fact found admission to the human mind.