criticism of successive generations has amply testified.

As we have said, Tycho Brahe, great observer as he was, could not
shake himself free from the Oriental incubus. He began his
objections, then, to the Copernican system by quoting the adverse
testimony of a Hebrew prophet who lived more than a thousand
years B.C. All of this shows sufficiently that Tycho Brahe was
not a great theorist. He was essentially an observer, but in this
regard he won a secure place in the very first rank. Indeed, he
was easily the greatest observing astronomer since Hipparchus,
between whom and himself there were many points of resemblance.
Hipparchus, it will be recalled, rejected the Aristarchian
conception of the universe just as Tycho rejected the conception
of Copernicus.

But if Tycho propounded no great generalizations, the list of
specific advances due to him is a long one, and some of these
were to prove important aids in the hands of later workers to the
secure demonstration of the Copernican idea. One of his most
important series of studies had to do with comets. Regarding
these bodies there had been the greatest uncertainty in the minds
of astronomers. The greatest variety of opinions regarding them
prevailed; they were thought on the one hand to be divine
messengers, and on the other to be merely igneous phenomena of
the earth's atmosphere. Tycho Brahe declared that a comet which
he observed in the year 1577 had no parallax, proving its extreme
distance. The observed course of the comet intersected the
planetary orbits, which fact gave a quietus to the long-mooted
question as to whether the Ptolemaic spheres were transparent
solids or merely imaginary; since the comet was seen to intersect