t motions of the heavenly bodies, on the principle of circular
movement. In the case of the sun and moon, Hipparchus succeeded in the
application of that theory, and indicated that it might be adapted to
the planets. Though never intended as a representation of the actual
motions of the heavenly bodies, it maintained its ground until the era
of Kepler and Newton, when the heliocentric doctrine, and that of
elliptic motions, were incontestably established. Even Newton himself,
in the 37th proposition of the third book of the "Principia," availed
himself of its aid. Hipparchus also undertook to make a register of the
stars by the method of alineations--that is, by indicating those which
were in the same apparent straight line. The number of stars catalogued
by him was 1,080. If he thus depicted the aspect of the sky for his
times, he also endeavoured to do the same for the surface of the earth
by marking the position of towns and other places by lines of latitude
and longitude.

[Sidenote: The writings of Ptolemy.]

[Sidenote: His great work: the mechanical construction of the heavens.]

Subsequently to Hipparchus, we find the astronomers Geminus and
Cleomedes; their fame, however, is totally eclipsed by that of Ptolemy,
A.D. 138, the author of the great work "Syntaxis," or the mathematical
construction of the heavens--a work fully deserving the epithet which
has been bestowed upon it, "a noble exposition of the mathematical
theory of epicycles and eccentrics." It was translated by the Arabians
after the Mohammedan conquest of Egypt; and, under the title of
Almagest, was received by them as the highest authority on the mechanism
and phenomena of the universe. It maintained its ground in Europe in the
same eminent position for nearly fifteen hundred years, justifying the
encomium of Synesius on the institution which gave it birth, "the divine
school of Alexandria." The Almagest commences with the doctrine that the
earth is globular and fixed in space; it describes the construction of a
table of chords and instruments for observing the solstices, and deduces
the obliquity of the ecliptic. It finds terrestrial latitudes by the
gnomon; describes climates; shows how ordinary may be converted into
sidereal time; gives reasons for preferring the tropical to the sidereal
year; furnishes the solar theory on the principle of the sun's orbit
being a simple eccentric; explains the equation of time; advances to the
discussion of the