A Dictionary of Greek and Roman biography and mythology. By various writers. Ed. by William Smith. Illustrated by numerous engravings on wood.

PTOLEMAEUS. PTOLEMAEUS. 577
would place him in agreement, or what he took for where, would avail himself of the rich materials
agreement, with the authority whom in his own collected by Greek investigators, especially from
mind he could not disbelieve. (EIalma and De- the time of Alexander; and this presumption is
lambre, opp. citt.; Weidler, Hist. Astron.; La- converted into a certainty by the information which
lande, Bibliogr. Astron.; Hoffinan,Lexic. Biblioyr.; Ptolemy gives us respecting the Greek itineraries
the editions named, except when otherwise stated; and peripluses which Marillus had used as authoFabric. Bibl. Graec., &c.) [A. De M.] rities. The whole question is thoroughly discussed
by Heeren, in his Commentaltio de Fontibus GeoTHE GEOGRAPHICAL SYSTEM OF PTOLEMY. graphicorum Ptolemaei, Tabularumque zis annexarum, Gotting. 1827, which is appended to the
The reCopalrpLK'Tp/7ty77oLs of Ptolemy, in eight English translation of his Ideen (Asiatic,rations,
books, may be regarded as an exhibition of the vol. iii. Append. C.). He shows that Brehmer has
final state of geographical knowledge among the greatly overrated the geographical knowledge of
ancients, in so far as geography is the science of the Phoenicians, and that his hypothesis is altodetermining the positions of places on the earth's gether groundless.
surface; for of the other branch of the science, the In examining the geographical system of Ptodescription of the objects of interest connected with lemy, it is convenient to speak separately of its
different countries and places, in which the work mathematical and historical portions; that is, of his
of Strabo is so rich, that of Ptolemy contains com- notions respecting the figure of the earth, and the
paratively nothing. With the exception of the mode of determining positions on its surface, and
introductory matter in the first book, and the latter his knowledge, derived from positive information, of
part of the work, it is a mere catalogue of the the form and extent of the different countries, and
names of places, with their longitudes and lati- the actual positions and distances of the various
tudes, and with a few incidental references to ob- places in the then known world.
jects of interest. It is clear that Ptolemy made a 1. The Mathematical Geography of Ptoleny.diligent use of all the information that he had Firstly, as to the figure of the earth. Ptolemy
access to; and the materials thus collected he assumes, what in his mathematical works he underarranged according to the principles of mathemati- takes to prove, that the earth is neither a plane
cal geography. His work was the last attempt surface, nor fan-shaped, nor quadrangular, nor
made by the ancients to form a complete geogra- pyramidal, but spherical. It does not belong to
phical system; it was accepted as the text-book the present subject to follow him through the deof the science; and it maintained that position tail of his proofs.
during the middle ages, and until the fifteenth The mode of laying down positions on the surcentury, when the rapid progress of maritime dis- face of this sphere, by imagining great circles passcovery caused it to be superseded. ing through the poles, and called meridians, because
The treatise of Ptolemy was based on an earlier it is mid-day at the same time to all places through
work by Marinus of Tyre, of which we derive which each of them passes; and other circles, one
almost our whole knowledge from Ptolemy him- of which was the great circle equidistant from the
self (i. 6, &c.). He tells us that Marinus was a poles (the equinoctial line or the equator), and
diligent inquirer, and well acquainted with all the the other small circles parallel to that one; and
facts of the science, which had been collected be- the method of fixing the positions of these several
fore his time; but that his system required cor- circles, by dividing each great circle of the sphere
rection, both as to the method of delineating the into 360 equal parts (now called degrees, but by
sphere on a plane surface, and as to the comnpu- the Greeks " parts of a great circle"), and imagining
tation of distances: he also informs us that the a meridian to be drawn through each division of
data followed by Marinlus had been, in many cases, the equator, and a parallel through each division of
superseded by the more accurate accounts of recent any meridian;-all this had been settled from the
travellers. It is, in fact, as the corrector of those time of Eratosthenes. What we owe to Ptolemy
points in the work of Marinus which were erro- or to Marinus (for it cannot be said with certainty
neous or defective, that Ptolemy introduces him- to which) is the introduction of the terms longitude
self to his readers; and his discussion of the (ciKos) and latitude (7rAdiros), the former to denecessary corrections occupies fifteen chapters of his scribe the position of any place with reference to
first book (cc. 6-20). The most important of the the length of the known world, that is, its distance,
errors which lie ascribes to Marinus, is that he in degrees, from a fixed meridian, measured along
assigned to the known part of the world too snall a its own parallel; and the latter to describe the
length from east to west, and too small a breadth position of a place with reference to the breadlh of
from north to south. He himself has fallen into the known world, that is, its distance, in degrees,
the opposite error. from the equator, measured along its own meriBefore giving an account of the system of Pto- dian. Having introduced these, terms, Marinus
lemy, it is necessary to notice the theory of Breh- and Ptolemy designated the positions of the places
mer, in his JEnldeckungen imnAlterthumn, that the they mentioned, by stating the numbers which.
work of Marinus of Tyre was based upon ancient represent the longitudes and latitudes of each. The
charts and other records of the geographical re- subdivision of the degree adopted by Ptolemy is
searches of the Phoenicians. This theory finds into twelfths.
now but few defenders. It rests almost entirely Connected with these fixed lines, is the subject
on the presumption that the widely extended com- of climates, by which the ancients understood belts
merce of the Phoenicians would give birth to of the earth's surface, divided by lines parallel to
various geographical documents, to which Marinus, the equator, those lines being determined according
living at Tyre, would have access. But against to the differenit lengths of the day (the longest day
this may be set the still stronger presumption, that was the standard) at different places, or, which is.
a scientific Greek writer, whether at Tyre or else- tihe same thing, by the different lengths, at different
VOL. III. P 1'