astronomic science seemed to awaken suddenly to a true inductive method,
and after him to fall into its old slumber for 300 years. In the
meantime Timocharis, Aristyllus, and Conon had each added their mites to
the discoveries of Eratosthenes: but to Hipparchus we owe that theory
of the heavens, commonly called the Ptolemaic system, which, starting
from the assumption that the earth was the centre of the universe,
attempted to explain the motions of the heavenly bodies by a complex
system of supposed eccentrics and epicycles. This has of course now
vanished before modern discoveries. But its value as a scientific
attempt lies in this: that the method being a correct one, correct
results were obtained, though starting from a false assumption; and
Hipparchus and his successors were enabled by it to calculate and
predict the changes of the heavens, in spite of their clumsy
instruments, with almost as much accuracy as we do now.

For the purpose of working out this theory he required a science of
trigonometry, plane and spherical: and this he accordingly seems to
have invented. To him also we owe the discovery of that vast gradual
change in the position of the fixed stars, in fact, of the whole
celestial system, now known by the name of the precession of the
equinoxes; the first great catalogue of fixed stars, to the number of
1080; attempts to ascertain whether the length of years and days were
constant; with which, with his characteristic love of truth, he seems to
have been hardly satisfied. He too invented the planisphere, or mode of
representing the starry heavens upon a plane, and is the father of true
geography, having formed the happy notion of mapping out the earth, as
well as the heavens, by degrees of latitude and longitude.

Strange it is, and somewhat sad, that we should know nothing of this
great man, should be hardly able to distinguish him from others of the