of much unpublished misapprehension--arises from the undeserved contempt
with which our books of astronomy too often treat the labours of
Ptolemy, Tycho Brahe, and others who advocated erroneous theories. If
the simple truth were told, that the theory of Ptolemy was a masterpiece
of ingenuity and that it was worked out by his followers in a way which
merits the highest possible praise, while the theory of Tycho Brahe was
placed in reality on a sounder basis than that of Copernicus, and
accounted as well and as simply for observed appearances, the student
would begin to realise the noble nature of the problem which those great
astronomers dealt with. And again, if stress were laid upon the fact
that Tycho Brahe devoted years upon years of his life to secure such
observations of the planets as might settle the questions at issue, the
student would learn something of the spirit in which the true lover of
science proceeds.

It seems to me, also, that far too little is said about the kind of work
by which Kepler and Newton finally established the accepted theories.
There is a strange charm in the history of those twenty years of
Kepler's life during which he was analysing the observations made by
Tycho Brahe. Surrounded with domestic trials and anxieties, which might
well have claimed his whole attention, tried grievously by ill-health
and bodily anguish, he laboured all those years upon erroneous theories.
The very worst of these had infinitely more evidence in its favour than
the best which the paradoxists have brought forth. There was not one of
those theories which nine out of ten of his scientific contemporaries
would not have accepted ungrudgingly. Yet he wrought these theories one
after another to their own disproof. _Nineteen_ of them he tried and
rejected--the twentieth was the true theory of the solar system. Perhaps
nothing in the whole history of astronomy affords a nobler lesson to the
student of science--unless, indeed, it be the calm philosophy with which
Newton for eighteen years suffered the theory of the universe to remain
in abeyance, because faulty measurements of the earth prevented his
calculations from agreeing with observed facts. But, as Professor
Tyndall has well remarked--and the paradoxist should lay the lesson
well to heart--'Newton's action in this matter was the normal action of
the scientific mind. If it were otherwise--if scientific men were not
accustomed to demand verification, if they wer