IV. Claudius Ptolemaeus
A famous Greek mathematician, astronomer, and geographer. He came from Ptolemaïs
Hermeiou (ruins at modern Menschie), in Upper Egypt, and lived and worked in the second
century A.D. The most important of his writings which have been preserved are: (
a)
Γεωγραφικὴ Ὑφήγησις (“instructions
for the drawing of maps”), a geographical work in eight books, the first of which
contains the principles of mathematical geography, the drawing of maps, and the calculation of
the longitudes and latitudes of places in the then known world; books ii.-vii. contain tables
of names of places in the maps described, arranged according to degrees and their
subdivisions; and book viii. contains an astronomical table of climates. This work is one of
the chief sources of our knowledge of ancient geography. It is edited by Nobbe
(Leipzig,
1845); and Müller
(Paris, 1883). (
b）
Μεγάλη Σύνταξις τῆς Ἀστρονομίας, usually known by its
Arabic name of
Almagest. Since the
Tetrabiblus, the work on
astrology, was also entitled
σύνταξις, the Arabs, to
distinguish the two, probably called the greater work
μεγάλη,
and afterwards
μεγίστη: the title
Almagest (Tabrir al
Magesthi) is a compound of this last adjective and the Arabic article. The
Almagest is divided into thirteen books. It treats of the relations of the
earth and heaven; the effect of position upon the earth; the theory of the sun and moon,
without which that of the stars cannot be undertaken; the sphere of the fixed stars, and those
of the five stars called
planets. The seventh and eighth books are the
most interesting to the modern astronomer, as they contain a catalogue of
the stars. This catalogue gives the longitudes and latitudes of 1022 stars, described by their
positions in the constellations. It seems that this catalogue is in the main really that of
Hipparchus, altered to Ptolemy's own time by assuming the value of the precession of the
equinoxes given by Hipparchus as the least which could be, some changes having also been made
by Ptolemy's own observations. Indeed, the whole work of Ptolemy appears to have been based
upon the observations of Hipparchus, whom he constantly cites as his authority. Ptolemy's
system of the heavens, which made the earth the fixed centre, was not superseded till the time
of Copernicus
(A.D. 1473-1543). The best edition of the
Almagest
is by Halma, 2 vols.
(Paris, 1813-16). (
c)
Τετράβιβλος Σύνταξις, generally called
Tetrabiblos,
or
Quadripartitum de Apotelesmatibus et Iudiciis Astrorum. With this goes
another small work, called
Καρπός, or
Fructus
Librorum Suorum, often called
Centiloquium, from its containing a
hundred aphorisms. Both of these works are astrological, and it has been doubted by some
whether they be genuine. But the doubt merely arises from the feeling that the contents are
unworthy of Ptolemy. (
d)
Κανὼν
Βασιλέων, a catalogue of Assyrian, Persian, Greek, and Roman sovereigns, with the
length of their reigns, several times referred to by Syncellus. (
e）
Φάσεις ἀπλανῶν ἀστέρων καὶ συναγωγὴ ἐπισημασειῶν,
De Apparentiis et Significationibus inerrantium, an annual list of sidereal
phenomena.
(f, g) De Analemmate and
Planisphaerium. These works
are obtained from the Arabic. The
Analemma is a collection of graphical
processes for facilitating the construction of sun-dials. The
Planisphere is a
description of the stereographic projection, in which the eye is at the pole of the circle on
which the sphere is projected. (
h)
Περὶ
ὑποθέσεων τῶν πλανωμένων,
De Planetarum Hypothesibus. This is a
brief statement of the principal hypotheses employed in the
Almagest for the
explanation of the heavenly motions. (
i)
Ἁρμονικῶν βιβλία γ́., a treatise on the theory of the musical scale, and the
most important ancient work on music next to that of Aristoxenus. Most of the works of Ptolemy
are contained in the edition of Halma in 4 vols.
(Paris, 1813-28). The principal
MSS. are at Vienna, Venice, and Mount Athos. This last is photographed and published by
Langlois
(Paris, 1866).
