Slide #119
TITLE: The world according to Ptolemy
DATE: A.D. 200
AUTHOR: Claudius Ptolemy
DESCRIPTION: The early period of cartography, from 4,000 B.C. to A.D.200
culminates with the contributions of the famous Greek scholar named Claudius
Ptolemy. Little is known, personally, of this pivotal man aside from the
general period during which he was active ca. A.D. 90 to 168 (during the
reigns of Hadrian and Antoninus Pius) and that he lived in, or near, Alexandria
Egypt. During the second century, Alexandria was not only the richest city
in the world, with regard to learned institutions and treasures of scholarship,
but also the wealthiest commercial place on the earth. It was a place where
seafaring people and caravans from all parts of the known world would use
to congregate, thereby providing the opportunity to collect knowledge of
far away lands and seas. In spite of such scant personal knowledge, Claudius
Ptolemy's writings have had a greater influence on cartography, and on geography
in general, than that of any other single figure in history.
While Ptolemy is most frequently associated with geography and cartography,
he also wrote important works in a number of other fields including astronomy,
astrology, music and optics. He composed a Table of Reigns, a chronological
list of Assyrian, Persian, Greek, and Roman sovereigns dating from Nabonasar
to Antoninus Pius, a biographical history of kingship. His Analemma was
mathematical description of a sphere projected on a plane, subsequently
known as an "orthographic projection," which greatly simplified
the study of gnomonics. His work entitled Planisphærium [the
Planisphere], described a sphere projected on the equator, the eye being
at the pole, a projection later known as "stereographic". But
there are two treatises for which Ptolemy is most celebrated. The first
of these treatises is his Magale Syntaxis (ca. A.D. 141), a composition
dealing with astronomy and mathematics, more commonly known by its hybrid
Greco-Arabic title, the Almagest, in which he lays down the foundation
of trigonometry and sets forth his view of the universe. Here he explains
his belief that the earth is a stationary sphere, at the center of the universe,
which revolves about it daily. While his proofs of the sphericity of the
earth are still accepted today as valid, Ptolemy rejected the theory of
the rotation of the earth about its axis as being absurd.
Ptolemy's approach to geography was strictly scientific and impersonal.
He was interested in the earth, all of it, not just the habitable part,
and tried to fit it into a scheme of the universe where it belonged. He
was also interested in the relationships between the earth and the sun,
the earth and the moon, in scientific cause and effect of climate; and above
all, he was concerned with a scientifically accurate portrayal of the spherical
earth in a convenient readable form. More than any one of the ancients,
Claudius Ptolemy succeeded in establishing the elements and form of scientific
cartography. This he did through his second great treatise, Geographike
Syntaxis, called by him, "the geographical guide to the making
of maps", and, in later centuries, shortened to simply Geographia,
or (incorrectly) Cosmographia. This work is actually the first general
atlas of the world to have survived, rather than a "Geography"
with a long textual introduction to the subject of cartography. Here for
the first time are documented the duties and responsibilities of the mapmaker,
his limitations, and the nature of the materials he was to work with. This
single treatise remained the standard work on geographical theory throughout
the Middle Ages, was not superseded as such with the 16th century, and constitutes
one of the fundamental tenentes of modern geodesy.
Although no original manuscript of this text has survived the ravages of
time, several manuscript copies, dating from the closing centuries of the
Byzantine Empire (ca. 11th century), still exist. These Byzantine copies
of the Geographia are comprised of eight "Books" which
Ptolemy introduces by supplying two very influential definitions - that
of chorography and geography. He defines chorography
as being selective and regional in approach, "even dealing with the
smallest conceivable localities, such as harbors, farms, villages, river
courses, and the liken. Geography, he said, differs from chorography
in that it deals with "a representation in picture of the whole
known world together with the phenomena which are contained therein".
As he proceeds to elaborate his definition of geography, it becomes apparent
that Ptolemy conceived that the primary function of geography was "mapmaking",
and that, to him, geography was synonymous with cartography. "It is
the prerogative of Geography," he said, "to show the known habitable
earth as a unit in itself, how it is situated and what is its nature; and
it deals with those features likely to be mentioned in a general description
of the earth, such as larger towns and great cities, the mountain ranges
and the principle rivers." No divergence from these fundamental matters
should be made, except for "features worthy of special note on account
of their beauty." Having thus introduced an elastic clause into an
otherwise rigid geographical code Ptolemy went on to elaborate the task
of the cartographer, which is to survey the world "in its just proportions,"
that is, to scale. Cartography is not an artistic endeavor according to
the Greek Scholar, but should be concerned with the relation of distance
and direction, and with the important features of the earth's surface which
can be indicated by plain lines and simple notations(enough to indicate
general features and fix positions).
For these and other reasons, Ptolemy knew mathematics to be an important
part of cartography. "It is the great and exquisite accomplishment
of mathematics to show all these things to the human intelligence."
With the aid of astronomy and mathematics, Ptolemy concluded, the earth
could be mapped as accurately as the heavens had been charted. In cartography,
said Ptolemy, one must contemplate the shape and size of the entire earth.
Its position under the heavens is extremely important, for in order to describe
any given part of the world one must know under what parallel of the celestial
sphere it is located. Otherwise how can one determine the length of its
days and nights, the stars which are fixed ovehead, the stars which appear
nightly over the horizon and the stars which never rise above the horizon
at all. All such data must be considered as important to the study and mapping
of the world.
The first Book of the Geographia is devoted primarily to theoretical
principles, including a discussion of globe construction, the description
of two map projections, and an extended, through amicable, criticism of
his primary source, Marinus of Tyre, "the latest of the geographers
of our time". Marinus, who flourished about A.D. 120, exerted considerable
influence on the development of mapmaking. He seems to have studied and
made astronomical observations in Tyre, the oldest and largest city of Phoenicia,
which, even at that late date, maintained important commercial relations
with remote parts of the world. This 'tutor' of Ptolemy had read nearly
all of the historians before him and had corrected many of their errors
(presumable errors relating to the location of places as contained in travelers'
itineraries). He had, moreover, edited and revised his own geographic maps,
of which at least two editions had been published before Ptolemy saw them.
The final drafts were nearly free from defects and his text, which we know
of only through Ptolemy, was so reliable, in Ptolemy's estimation, that
"it would seem to be enough for us to describe the earth on which we
dwell from his commentaries alone, without other investigations." According
to Ptolemy, the most significant feature of the maps of Marinus was the
growth of the habitable world and the changed attitude toward the uninhabited
parts. Marinus was a good man, in Ptolemy's estimation, but he lacked the
critical eye and allowed himself to be led astray in his scientific investigations.
According to Ptolemy, even Marinus had made mistakes, either because he
had consulted "too many conflicting volumes, all disagreeing,"
or because he had never completed the final revision of his map. Whichever
it was, the map needed correcting - by Ptolemy, of course. However, Marinus'
treatise on geography, with its maps, should still be ranked among the most
important of the lost documents of the ancients, if for no other reason
than that it was the foundation upon which Claudius Ptolemy built.
In another chapter in Book I, Ptolemy wrote that there are two ways of making
a portrait of the world; one is to reproduce it on a sphere, and the other
is to draw it on a plane surface. Each method has its advantages and disadvantages.
"When the earth is delineated on a sphere, it has a shape like its
own, nor is there any need of altering [it] at all." However, it is
not easy to provide enough space on a globe for all of the details which
should be included on it; moreover, if it is large enough to contain everything
that should be drawn on it, the globe would be too large for the eye to
encompass. Ptolemy then continues to give specific instructions on how to
construct a globe properly.
If the second method of drawing the earth is used, that is, if the spherical
earth is projected onto a plane surface, certain adjustments are obviously
necessary. Marinus had given this matter considerable thought, rejecting
all previously devised methods of obtaining congruity on a flat map; yet,
according to Ptolemy he had finally selected the least satisfactory method
of solving the problem. Marinus had laid out a grid of strait lines equidistant
from one another for both his parallels of latitude and meridians of longitude.
This was contrary to both truth and appearance, and the resulting map was
badly distorted with respect to distance and direction, for if the eye is
fixed on the center of the quadrant of the sphere which we take to be our
inhabited world, it is readily seen that the meridians curve toward the
North Pole and that the parallels, though they are equally spaced on the
sphere, give the impression of being closer together near the poles. Ptolemy
was well aware that it would be desirable to retain a semblance of spherical
proportions on his flat map, but at the same time he decided to be practical
about it. To avoid, or at least to lessen these errors by Marinus, Ptolemy
proposed to employ what is now called a conical projection, i.e., to project
the map, with equidistant parallels, on a conical surface developed around
the axis of the earth, and passing through the parallels of Rhodes
and Thule. When such a conical surface is extended on a plane, a
network with circular parallels and rectilinear, converging meridians arise.
Lest the proportions of certain parts of the mapped territory should be
too much deformed, only the northern or the southern hemispheres should
be laid down on the same map by this projection, which is consequently inconvenient
for maps embracing the whole earth. Ptolemy only rigorously applies the
conical projection to the northern part of his map of the world. To represent
the known parts of the southern hemisphere on the same sheet, he describes
an arc of a circle parallel to the equator, and at the same distance to
the south of it, as Meroe [Mæroe ] is to the north, and then
divides this arc in parts of the same number and size, as on the Parallel
of Meroe. The network is then obtained by joining the intersections
to corresponding points on the equator.
Ptolemy's exhaustive criticism of the imperfect methods of drawing maps
adopted by Marinus, would lead to the expectation that he himself would
have used some of his own recommended projections in constructing his maps.
But such was not the case. Because while Ptolemy employs his conical projection
in his first general world map, for the remaining twenty-six special regional
maps he uses the rectangular projection of Marinus with due observance
of the ratio between the longitude and latitude at the base of the map.
This inconsistency seems to have astonished his publishers in the 15th and
16th centuries. With one exception (an Italian translation by Berlinghieri),
every editor of Ptolemy's Geographia has published, not the original
maps, but a modification of them by Nicolaus Germanus (Donis), who, with
praiseworthy exactness and without any further alterations, reproduced the
originals, on a projection with rectilinear, equidistant parallels and meridians
converging towards the poles.
Book II of the Geographia opens with a prologue "of the particular
descriptions", which is to say, the maps he was about to present, and
a general statement of his mapmaking policy. There is also an introduction
to data collection, evaluation, preparations for drawing, how and in what
order to mark boundaries, and how to use the appended tables. Books II-VI
and the first four chapters of Book VII are devoted to a complete catalogue
of some 8,000 inhabited localities laid down in the twenty-six special maps
of the geography. For every place-name, estuaries sources, mountains, promontories,
peninsulas, etc., mentioned in the catalogue/table, latitude and longitude
(in degrees) is given. It is an exception when geographical or descriptive
remarks are added to this bare enumeration of names. What is remarkable
and president-setting is the organization of these tables. Unlike Marinus
who listed longitude on one page and latitude on another, Ptolemy began
the tradition of listing the positional coordinates together and in a usable
system that was practical to follow.
The latitude and longitude assigned to well-known places were fairly accurate
since the traditional accounts concerning them agreed and more exacting
measurements/observations had been taken; but the places that were little
known, or about which there was considerable uncertainty, presented a major
problem to geographers like Ptolemy. When traveling overland it is usually
necessary to diverge from a straight line course in order to avoid inevitable
land-barriers; and at sea, where winds are changeable, the speed of a vessel
varies considerably, making it difficult to estimate over-water distances
with any degree of accuracy. Nevertheless Ptolemy concluded that the most
reliable way of determining distances was by astronomical observation, and
by no other method could one expect to fix positions accurately. Traditional
information regarding distances should be subordinated, especially the primitive
sort, for tradition varies from time to time, and if it must enter into
the making of maps at all, it is expedient to compare the records of the
ancient past with newer records, "deciding what is credible and what
is incredible". Therefore if a geographer were obliged to fall back
on the reports of travelers, he should exercise some discrimination in his
choice of authorities. Finally, Ptolemy thought, about all one could do
was to locate unfamiliar places as accurately as possible with reference
to well-known places, in as much as it is advisable on a map of the entire
world to assign a definite position to every known place, regardless of
how little is known about it. This Ptolemy did in marginal notations, leaving
spaces for any necessary corrections.
The fifth chapter of Book VII contains a description of the map of the world,
together with an enumeration of the oceans and of the more important bays
and islands. The Indian Ocean, which is assumed to be bordered on the south
by an unknown continent, uniting southern Africa with eastern Asia, is stated
to be the largest sea surrounded by land. The Atlantic Ocean is not even
mentioned among the seas. It is remarkable that such questions never seemed
to have occurred to Ptolemy, as: What is there to be found beyond Serica
and Sinarum Situs ? What could be found to the north of Thule,
or to the south of Agysimba and Cape Prasum : Where would
you arrive if you sailed westward from the Fortunate Islands ?
In the eight and last Book of the Geographia, Ptolemy returned to
the business of discussing the principles of cartography, mathematical,
geographical and astronomical methods of observation, and, in some cases
(manuscript or printed copies) there follow short legends for each of the
special maps - ten for Europe, four for Africa and twelve for Asia - mentioning
the countries laid down on each plate, describing the limits, and enumerating
the tribes of each country and its most important towns. It is these legends
which, in some editions, have been placed on the reverse of the maps, and
they appear to have been originally intended for that purpose. In addition,
a description of a projection of the inhabited hemisphere on a plane, by
which it could retain its circular outline, or globular aspect is also given.
Ptolemy himself never actually employed this manner of projection, which
has since, through more or less modified, been preferred by geographers
for maps representing one of the hemispheres.
Those scholars who have argued that Ptolemy's original text contained no
maps have neglected careful study of this Book. In Chapter Two Ptolemy said,
"It remains for us to show how we set down all places, so that when
we divide one map into several maps we may be able to accurately locate
all of the well-known places through the employment of easily understood
and exact measurements." On the other hand, some scholars even go so
far as to say that maps were already drawn before certain portions of the
text was addressed, so that they could be used as models for the completion
of other portions of the text.
Ptolemy went on to explain how the more common faults of map makers might
be avoided. For instance, in a single map embracing the entire earth, he
said, there is a tendency to sacrifice proportion, that is, scale, in order
to get everything on the map. The better known regions have many place-names,
while the lesser known have few, and, unless the map is carefully drawn,
it will have some crowded, illegible areas, and some where distances are
unduly extended. Some map makers have a tendency to exaggerate the size
of Europe because it is most populous, and to contract the length of Asia
because little is known about the eastern part of it. And some cartographers
surround the earth on all sides with an ocean which, according to Ptolemy
are "making a fallacious description, and an unfinished and foolish
picture".
The obvious way to avoid crowding, Ptolemy said, is to make separate maps
of the most populous regions or sectional maps combining densely populated
areas with countries containing few inhabitants, if such a combination is
feasible. If several regional maps are made to supplement the general world
map, they need not "measure the same distance between the circles",
that is, be drawn to the same scale, provided the correct relation between
distance and direction is preserved. Ptolemy repeated that it would be not
too far from the truth if instead of circles we draw straight lines for
meridians and parallels. As for his own policy, he said, "in the separate
maps we shall show the meridians themselves not inclined and curved but
at an equal distance one from another, and since the termini of the circles
of latitude and of longitude of the habitable earth, when calculated over
great distances do not make any remarkable excesses, so neither is there
any great difference in any of our maps". These things being so, he
continued, "let us begin the task of a division such as the following:
"We will make ten maps for Europe; we will make four maps for Africa;
for Asia we will make twelve maps to include the whole, and we will state
to which continent each map belongs, and how many and how great are the
regions in each..." The latitude of each place would be given as well
as the length of the longest day in equinoctial hours. The longitudes would
be determined from the meridian of Alexandria, either at sunrise or sunset,
calculating the difference in equinoctial hours between Alexandria and point
two, whatever it might be.
While there is little doubt still lingering that Ptolemy's text was originally
illustrated by maps, it is not altogether certain that the maps found today
in existing copies of the Geographia are indeed similar to those
of the original series of maps, since the latter have not survived for comparison.
The reason for this doubt lies in the question of authorship of the maps
which accompany extant copies. Did Ptolemy actually design and construct
the maps himself, were they made by a draftsman working under his supervision,
or were they added, perhaps as late as 1450, by an energetic editor who
thought the text needed some graphic emendation? Ptolemy does not state
specifically in his text whether he personally made any maps, and proponents
of the theory that Ptolemy made no maps for this Geographia base
their case on the notation in two of the existing manuscript copies, that
a cartographer named Agathodæmon of Alexandria was the author of the
accompanying map(s). From these same manuscripts it is stated that "he
drew them according to the instructions in the eight books of Claudius Ptolemy".
However, this statement has never been dated and, confusingly, Agathodæmon's
single-sheet world map employs a projection unlike any proposed by Ptolemy's
text. This particular world map is usually found at the end of Book VII,
preceded by three chapters containing some practical advice, a general description
of all known areas of the world and the three principle seas (the Mediterranean,
the Caspian and the Indian Ocean), with their bays and islands, and instructions
for drawing a sphere and maps on a plane surface. Many scholars ascribe
these three chapters to Agathodæmon, as the descriptive text for his
map. However, the authorship of the other twenty-six maps is still in doubt.
To further confound the issue, all of the other manuscript copies of the
Geographia that are accompanied by maps differ one from another, presenting
two basic versions. According to Leo Bagrow, one version, A, contains twenty-six
large maps included in the eighth Book of the text, each folded in half
and, on the back, having a statement of the region portrayed, its bounds
and a list of principle towns. The geographical coordinates of these towns
are given, not in degrees, but in time; the longitude is expressed in hours
and minutes corresponding to the distance from the meridian of Alexandria
(one hour = 15 degrees, one minute = 15 minutes of a degree), and the latitude
is expressed in terms of the length of the longest day, in hours and minutes
(the greater the distance from the equator, the longer the day in summer).
The other version, B, contains sixty-four maps distributed throughout the
text, vice collected together in one place. In some manuscripts of the B-version,
and in those without maps, the text from the backs of the maps are combined
together in a special edition, divided into chapters numbered 3-28. There
follows supplementary information on satrapies, provinces, etc. and a table
of the latitudes and longitudes of each map.
Over and above these maps, those manuscripts with maps, both A- and B-versions,
are additionally illustrated with a universal map of the entire known world
at Ptolemy's time, either on one sheet or four sheets; only very rarely
are both world maps found together. Of the Greek manuscripts of the Geographia,
as a whole or in part, known today, eleven of the A-version and five of
the B-version have maps. Some of the manuscripts without maps contain references
to accompanying maps, since lost, and in others, spaces have been left for
maps to be inserted. It is no less difficult, also, to determine when the
maps of the two versions (A and B)were made. Certain indications point to
the Byzantine period, with the exception of Agathodæmon's single-sheet
world map. But, again, when they were constructed - totally and faithfully
copied from the originals, or constructed from Ptolemy's instructions but
without benefit of original models - is significant in trying to determine
the degree of similarity to their 'prototype' and the possibility of additions
or corrections based upon more contemporary knowledge. It is noteworthy
here to point out that, regardless of when these existing manuscript reproductions
were made, they somehow escaped the pictorial fancies such as sketches of
animals, monsters, savages, ships, kings, etc. as adorn the manuscript maps
of the Middle Ages and many of the printed maps of the 16th century.
The illustration shown above gives a diagram of the parts of the known world
embraced by each special map found in Ptolemy's Geographia. It demonstrates
how Ptolemy's world had been systematically divided into twenty-six regions,
each of which is mapped on a separate sheet. Generally these sheets are
of about the same size, but the scales vary according to the space required
for the legends. As this diagram shows, each regional map would encompass,
besides its own proper territory, some parts of the neighboring countries.
But, as is also usual in modern atlases, these neighboring areas of the
map are only roughly sketched, while the principle area is shown in full
detail. As mentioned earlier, the original text called for twenty-six regional
or special maps, which in all extant manuscript copies bear a strong family
resemblance and are laid down on the projection apparently used by Marinus
in the form of isosceles trapezoids. Some of the other conspicuously modern
conventions include the previously noted lack of ornamentation, his method
of differentiating land and water, rivers and towns, by means of either
hachures or different colors, and his use of 'standardized' symbols all
of which is accepted at first glance without a thought being given to the
origin of the technique. This particular projection shown of the general
map of the habitable world, the one believed to be employed by Ptolemy in
his original general map, is laid down in the lazy man's projection he talked
about, the modified conic instead of the spherical projection
that he recommended for a faithful delineation of the earth's surface.
Slides #119, A thru F show various renditions of the Ptolemaic world-picture.
As with modern maps, Ptolemaic maps are oriented so that North would be
at the top and East at the right, because better known localities of the
world were to be found in the northern latitudes, and on a flat map they
would be easier to study if they were in the upper right-had comer. The
meridians are spaced from each other "the third part of an equinoctial
hour, that is, through five of the divisions marked on the equator".
In other words, the total span of twelve hours, representing the length
of the habitable world, was to be partitioned by a series of thiry-six meridians
spaced five degrees apart at the equator and converging at the North Pole.
The meridians in the southern hemisphere are extended from the equator at
the same angle as those above it, but instead of converging at the South
Pole they terminated at the parallel 8° 25' below the equator.
Displayed on the left-had margin of these world maps are seven Clima
[Klima] and Parallel Zones. In Ptolemy's time, the latitude,
or distance from the equator, was generally astronomically calculated from
the length of the longest and the shortest day. The earth was accordingly
divided into a number of zones, parallel to the equator and within which
these days had a certain length, for instance of 12 -13, or 15 -16 hours.
The concept of the division of the earth into zones began as early as the
6th century B.C. with a Greek scholar named Permenides of Elea and were
called climates from the Greek word meaning inclination. Different
from what is now accepted as the meaning, this word in ancient maps had
a purely geographical, not a meteorological significance, although they
also perceived that the climate of a region was somewhat related to its
distance from the equator. The lines that separate the Climata were
termed Parallels. As can be seen from these world maps, Ptolemy divided
the northern hemisphere into twenty-one parallels, noted, again, in the
margin of this maps. The parallel bounding the southern limit of the habitable
world is equidistant from the equator in a southerly direction as the parallel
through Meroe is distant in a northerly direction. Ptolemy laid down
his parallels from the equator to Thule. The twenty-one parallels
are spaced at equal lineal intervals and each one is designated by (1) the
numberof equinoctial hours and fractional hours of daylight on the longest
day of the year and (2) the number of degrees and minutes of arc north of
the equator. For example, the first parallel of latitude north of the equator
was distant from it "the fourth part of an hour" and "distant
from it geometrically about 4°15"'. One other parallel is added
south of the equator, identified with the Rhaptum promontory and
Cattigara and about 8° 25' distant from "The Line".
All of the parallels north of the equator are located theoretically with
the exception of three: Meroe, Syene and Rhodes. The first
one, Clima I per Meroe, (so called because it passes through Meroe,
near modern Shendi, a city of Africa at 17° N latitude) was established
traditionally as 1,000 miles below Alexandria and 300 miles from the torrid
zone; it was also known as the royal seat and principal metropolis of Ethiopia
[Africa].
Clima II per Syene passes through Syene, the modern Aswan,
which was still considered as one of the very few scientifically located
parallels because of the fact that it lay on the line of the Summer Tropic
and was always included in any discussion of the parallels; Clima IV
per Rodo passes through Rhodes, which had become the most popular
parallel of all and was located by common consent at 36° N.; Clima
VI per Rondo passes through Pontus [the Black Sea], and so on.
The numbers on the right of the Clima give the number of hours in the longest
day at different latitudes, increasing from 12 hours at the equator to 24
hours at the Arctic Circle.
Overall Ptolemy's world-picture extended northward from the equator a distance
of 31,500 stades* to 63° N at Thule, and southward to
a part of Ethiopia named Agysimba and Cape Prasum at
16° S latitude, or the same distance south as Meroe was north.
The "breadth" of the habitable world according to Ptolemy then
equates to 39,500 stades [4,500 miles]. It is remarkable that, while
his map is consistently mentioned as reflecting the entire inhabited portion
of the globe, there is no indication by Ptolemy on any of his world maps
of habitation south of Agysimba, though there is some hint of his
belief/knowledge to the contrary in his criticism of Marinus on this point.
Marinus estimated that the length of the known habitable world, i.e. the
distance between the Fortunate Islands [Canary-Madiera Island group]
in the west, and Cattigara [Borneo?] in the east, to be a distance
of 15 hours of longitude, 230° (11,250 miles) at the equator. Ptolemy
"corrected" this length to 180° (9,000 miles), still 50°
(2,500 miles) too long, an error arising from using the Fortunate Islands
as his prime meridian which he placed about seven degrees (350 miles) too
far to the east. Contributing to this mistake was Ptolemy's (and Marinus')
rejection of the surprisingly accurate calculation of the circumference
of the earth, made by Eratosthenes (276 -196 B.C .) of 252,000 stadia
[25-28,000 miles]. Instead Ptolemy/Marinus adopted the figure derived by
Posidonius (135 - 50 B.C.) of 180,000 stadia [18,000 miles] and applied
it to the distance measurements available to him, concluding that Europe
and Asia extended over one-half of he globe; in reality they cover only
130°. Similarly he showed the length of the Mediterranean as 62°,
whereas, in reality it is only 42°. The eastward extension of Asia is
also exaggerated, measuring about 110° from the coast of Syria to the
outermost limits of China, instead of the true distance of about 85°.
It has been repeatedly pointed out that the distances set down by Ptolemy
in his tables for the Mediterranean countries, the virtual center of the
habitable world, are erroneous beyond reason, considering the fact that
Roman Itineraries were accessible. But were they really available
to non-military men such as Marinus and Ptolemy? It is very unlikely, in
view of the secrecy attached to all maps and surveys of the Roman Empire.
If, as seems to be the case, Marinus depended for maritime distances largely
from the writings of Timosthenes of Rhodes (the admiral of Ptolemy Philadelphus,
who flourished about 260 B.C.), there must have been very little information
available to a scientist and scholar such as Claudius Ptolemy, who seems
to have had no political or military motive, but only seemed interested
in the advancement of learning as justification for his investigations.
And it is highly probable that Ptolemy the astronomer, who is usually discredited
by later geographers because of his methods and the kinds of information
he compiled, had no more standing among some of his influential contemporaries
than he would today in the most approved geographical circles of the civilized
world.
The geographical errors made by Ptolemy in his text and maps constitute
the principal topic of many scholarly dissertations. Yet most of his errors
arose from nothing more than a dearth of information. He lacked enough reliable
facts. The whole world lacked the fundamental data necessary to compile
an accurate map. The only good reason for discussing a few of the glaring
faults of the Geographia is that it was the canonical work on the subject
for more than 1400 years. Geographers of the 15th and 16th centuries relied
on it so heavily, while ignoring the new discoveries of maritime explorers,
that it actually exerted a powerful retarding influence on the progress
of cartography. The Geographia was both a keystone and a millstone,
a pioneering effort that outlived its usefulness. His hypothetical map was
excellent but his world of reality was faulty.
Paradoxically, Ptolemy's eastward extension of Asia, reducing the length
of the unknown part of the world, coupled with his estimate of the circumference
of the earth, was his greatest contribution to history if not cartography.
The earth was only 18,000 miles around at the equator; Poseidonius had stated
it, Strabo substantiated it, and Ptolemy perpetuated it on his maps. This
"shorter distance" that a mariner would have to travel west from
the shores of Spain in order to reach the rich trading centers of Asia may
have contributed to Columbus' belief, or that of his royal sponsors, that
they could compete with their rival neighbors, Portugal, in the newly opened
sea-trade with India by sailing west. While Ptolemy's map is based upon
the theory that the earth is round, it bares repeating that it is to his
credit that he depicts only that half of its surface which was then known,
with very little attempt to speculate on or "fill-in" the unknown
parts with his imagination.
Ptolemy provides a descriptive summary in his text in which he tells us
that the habitable part of the earth is bounded on the south by the unknown
land which encloses the Indian Sea and that it encompasses Ethiopia south
of Libya, called Agisymba. On the west it is bounded by the unknown land
encircling the Ethiopian Gulf of Libya and by the Western [Atlantic]
Ocean which borders on the westernmost parts of Africa and Europe;
on the north, "by the continuous ocean called Ducalydonian and
Sarmantian which encompasses the British islands, the northernmost
parts of Europe and by the unknown land bordering on the northernmost parts
of Greater Asia; that is to say, on Sarmatia, Scythia and Serica".
There are three seas surrounded by land. Of these, the Indicum Mare [Indian
Ocean] is the largest, Our Sea [the Mediterranean] is the next and
the Hyrcanian [Caspian] is the smallest. Among the most noted islands of
the world are Taprobane [Ceylon/Sri Lanka and, perhaps, Sumatra],
the Island of Albion [Britain], the Golden Chersonesus [the
Crimea], Hibernia [Ireland], Peloponnesus [Morea]; then come
Sicily, Sardinia, Corsica (also called Cyrnos), Crete and Cyprus.
More specifically, Ptolemy's knowledge concerning the fringes of the habitable
world and civilization was broader than earlier writers, such as Strabo,
but in some respects it was a little confused. In the northern regions,
for example, he had been ill-advised with regard to Ireland, and positioned
it further north than any part of Wales; likewise, Scotland was twisted
around so that its length ran nearly east and west. The Scandinavian peninsula
was shown as two islands, Scandia and Thule. The northern
coast of Germany beyond Denmark, Cimbrica Chersonese, is shown as
the margin of the Northern Ocean, and running in a general east-west
direction. The northern coast of Asia is not shown at all.
The southern limit of the habitable world had been fixed by Eratosthenes
(Slide #112) and Strabo at (Slide
#115) the parallel through the eastern extremity of Africa, Cape Guardafiri,
the cinnamon-producing country and the country of the Sembritæ
[Senaai]. This parallel also passed through Taprobane usually considered
the southernmost part of Asia. The extent of Africa below this parallel
is left an unanswered mystery.
Ptolemy records, following Marinus, the penetration of Roman expeditions
to the land of the Ethiopians and to Agisymba, a region of
the Sudan beyond the Sahara desert, perhaps the basin of Lake Chad, and
he supplied other new information regarding the interior of North Africa.
As to the source of the Nile, both Greeks and Romans had tried to locate
it, but without success. The Emperor Nero had sent an expedition into Upper
Egypt, and it had penetrated as far as the White Nile, about 9° N latitude.
But the source had not been reached. Ptolemy stated that the Nile arose
from two streams, the outlets of two lakes a little south of the equator,
which was closer to the truth than any previous conception, or any later
one until the discovery of the Victoria and Albert Nyanza in modern times.
The eastern coast of Africa was better known than the western, having been
visited by Greek and Roman traders as far as Rhapta [Rhaptum Promontory
opposite Zanzibar ?] which Ptolemy placed at about 7° S. To this he
added a bay extending to Cape Prasum [Delgado?] at 15.5° S. On
the same approximate parallel he located the region called Agisymba,
inhabited by Ethiopians and abounding in rhinoceri, supposedly discovered
by Julius Maternus, a Roman general. With Thule as the northern limit
of Ptolemy's habitable world, he thus extended the breadth of this world
from less than 60° (Eratosthenes and Strabo) to nearly 80°.
According to Greek tradition, an extension of 20° in the width of the
habitable world called for a proportionate increase in its length. Ptolemy
extended the west coast of Africa with a free hand, and even though he reduced
the bulge made by Marinus more than half, it was still way out of control.
A more obvious area to stretch the length of the world was in eastern Asia
where there was every likelihood of additional territory yet unexplored.
The silk trade with China had produced rumors of vast regions east of the
Pamir and Tian Shan, hitherto the Greek limits of Asia. Ptolemy took very
little stock in the seven-month's journey to Sera [China] and refused
to follow Marinus who said the distance was 3,620 miles from the Stone
Tower to Sera, but instead cut the distance in half without presenting
any critical evidence/argument.
Ptolemy's knowledge of the vast region from Sarmatia to China was,
however, better than that of previous map makers. He shows, for the first
time, a fairly clear idea of the great north-south dividing range of mountains
of Central Asia, which he called Imaus, but he placed it nearly 40°
too far east and made it divide Scythia into two parts: Scythia
Intra Imaum and Scythia Extra Imaum Montem ["Within Imaus"
and "Beyond Imaus"]. Asia and Africa are extended considerably
to the east and south, far more so than on any previous maps, but not without
cause. These distortions represented an actual extension of geographical
knowledge and are doubtless based on exaggerated reports of distances traveled.
All such information was of doubtful origin, and in laying down the coastline
of Eastern Asia, Ptolemy ran the line roughly north and south. Instead of
continuing it to the Land of the Linæ [seacoast of China] he
curved it around to the east and south, forming a great bay, Sinus Magnus
[roughly the Gulf of Siam]. Continuing it around to the south until it joined
Terra Incognita at the southern limit of the habitable world, he
made a lake of the Indicum Mare [Indian Ocean]. To judge, therefore,
from the map, Ptolemy discarded both the older Greek belief that the earth
was surrounded by water, and Herodotus' description of the Phoenician's
circumnavigation of Africa. Yet this Ptolemaic theory was later mysteriously
"re-interpreted" by Martin Waldseemüller in 1507 (Slide #312) and again by Gerard Mercator
in 1569 as a belief by Ptolemy in an all encircling great ocean. That paradox
notwithstanding, though, Ptolemy's depiction of a southern Afro-Asian continent
and a land-locked Indian Ocean provided little comfort during the intervening
1,300 years to those early explorers, and later the Portuguese, in their
attempts to find an all water route to India.
Many faults appear in Ptolemy's picture of southern Asia, although for more
than a century commercial relations between western India and Alexandria
had been flourishing. An important document entitled The Periplus of
the Erythræan [Indian] Sea (ca. A.D. 80) containing sailing
directions from the Red Sea to the Indus and Malabar, indicated that the
coast from Barygaza [Baroch] had a general southerly trend down to
and far beyond Cape Korami [Comorin], and suggested a peninsula in
southern India. Ptolemy, apparently following Marinus, ignored this document,
or else never saw it because the shape of his India is unduly broadened
and foreshortened. Eratosthenes, via Strabo, reported that the southern
capes of India lay opposite to Meroe. For the most part, the lands
beyond the Ganges were not well known until a thousand years later when
the brothers Polo first acquainted western Europe with the existence of
a number of large islands in that part of the world. And there were no good
maps of the East Indian Archipelago until after the Portuguese voyages to
the Indies. The legendary island of Taprobane [Sri Lanka, and possibly
Sumatra], whose size had always been grossly over-estimated, was not improved
by Ptolemy, who extended it through 15° of longitude and 12° of
latitude, making it about fourteen times as large as it really was and extending
its southerly tip more than 2° below the equator.
Even the more familiar territory of the Mediterranean basin demonstrated
that insufficient contemporary knowledge was available and Ptolemy erred
in many important cartographical details. His Mediterranean is about 20°
too long, and even after correcting his lineal value of a degree it was
still about 500 geographical miles too long. His Mare Nostrum, from
Marseilles to the opposite point on the coast of Africa, is 11° of latitude
instead of the actual 6.5°. The best known parallel of latitude (36°
N) was not a parallel at all as Ptolemy drew it. Leaving the habitable world
from the Strait at the Pillars of Hercules to the Gulf of Issus,
it passed through Caralis in Sardinia and Lilybaeum in Sicily (30°
12' and 37° 50' N). Carthage is positioned 1° 20' south of
the parallel of Rhodes; actually it is one degree north of it. Byzantium
is placed in the same latitude as Massilia, which made it more than
two degrees north of its true position. This particular error threw the
whole Euxine Pontus [Black Sea], whose general form and dimensions
were fairly well known, too far north by the same amount, over 100 miles.
His exaggeration of the Palus Mæotis [Sea of Azov ] plus the
fact that he switched its direction to north-south, brought its northern
extremity, the Tanais [Don] estuary, as high as 54° 30', the
true latitude of the south shore of the Baltic Sea! However, he was apparently
the first of the ancient geographers to have a fair conception of the relations
between the Tanais, usually considered the northern boundary between
Europe and Asia, and the Rha [Volga], which he said flowed into the
Caspian Sea. Ptolemy was also the first geographer, excepting Alexander
the Great, to return to the correct view advanced by Herodotus and Aristotle,
that the Caspian was an inland sea without communication with the ocean
(the Christian medieval cartographers were a long time in returning to this
representation of the Caspian).
In spite of the egregious errors on all of Ptolemy's maps, his atlas was
indeed an unsurpassed masterpiece for almost 1,500 years. Its wealth of
detail still constitutes one of the most important sources of information
for the historian and student of ancient geography. This is especially true
in the study of the earliest tribes that encompassed the Roman Empire in
the first century of the Christian era, who were at that time barbarians,
but who later bore the burden of civilization in Europe. To be sure, there
are other geographical fragments, individual maps and charts, isolated examples
of the best in Greek, Roman, and Arabic cartography, but Ptolemy's Geographia
is the only extant geographical atlas which has come down to us from the
ancients. There is nothing in the literature to indicate that any other
such systematic collection of maps was ever compiled, with the exception
of the maps of Marinus, about which almost nothing is known, save what Ptolemy
has mentioned.
The form of his atlas and the maps themselves are the prototypes of modern
mapmaking. Many of the legends and conventional signs that he used are still
employed by cartographers with only slight modifications. He originated
the practice of orienting maps so that North is at the top and East to the
right, a custom so universal today that many people are lost when they try
to read a map oriented any other way. His map projections, the conical
and modified spherical, as well as the orthographic and stereographic
systems developed in the Almagest, are still in use. The listing
of place-names, either in geographical or alphabetical order, with the latitude
and longitude of each place to guide the search, is not so different from
the modern system of letters and numerals employed to help the reader, a
little convenience that is standard on modern maps and Ptolemaic in origin.
During the intellectual narrow-mindedness of the Middle Ages even Ptolemy
and his methods of map construction were forgotten, at least in the west.
Ptolemy's works were, however, thriving and contributing valuable insight
to knowledgeable Arabs and those having access and understanding of the
Arab or Greek language (it was only in the Islamic states and in these languages
that the works of the Alexandrian scientist were preserved (Slides
#212, #213, 214-17 , lbn Said, al-lstakhri, Ibn Hauqal,
al-Kashgari, etc.). In Christian Western Europe, instead of Ptolemaic-like
maps that are clear, intelligible, drawn in proper proportion and referenced
by astronomical observations, maps were constructed without as sense of
proportion (e.g., medieval T-O maps), covered with figures of princes in
mantle and crown, blank spaces filled with monsters and fantastic legends
and often were produced merely as thematic illustrations/ornamentation for
some religious text or local church. There were some rare exceptions that
broke with this tradition and portrayed a more "scientific", though
still non-Ptolemaic, outlines of the known world - i.e., the Cottonian
Map, the Catalan Atlas, Fra Mauro's Map and, of course
the nautical or portolan charts.
The presently known version of Ptolemy's works began to surface when the
Byzantine monk Maximos Planudes (1260 - 1310) succeeded in finding and purchasing
a manuscript copy of the Geographia. This copy, which is now in the
Vatican Library (Vat.Gr.177), contained no maps, but only Agathodæmon's
remarks on the construction of his world map. Planudes constructed a map
based upon the instructions found in Ptolemy's eight books and subsequently,
through Athanasios, Patriarch of Alexandria, had a copy of the Geographia,
with maps made for Emperor Andronicus III. This particular copy has not
been recovered, however another copy attributed to Planudes is preserved,
in part, in the monastery of Vatopedi on Mount Athos.
Another scholar of the Byzantine age is known to have been interested in
Ptolemy's Geographia - the noted polyhistor Nikephoras Gregoras (1295
- c. 1359), who added various notes or comments, generally in the margins
to the text or maps. He is also credited with the four-page world map found
in some manuscripts, chiefly the B-version. It was also during this time,
the 14th century, that the twenty-six maps of the A-version were divided
up into sixty-four. Thus there was an "evolution" of the Geographia,
originating with the creation of Ptolemy and gradually developed in various
forms by three or four different hands/minds over the course of twelve centuries,
reaching the 14/15th century in a doubtful state of the original, especially
the maps.
In 1400 a Greek manuscript copy of the A-version (twenty-six maps) was obtained
from Constantinople by the Florentine patron of letters, Palla Strozzi,
who persuaded Emmanual Chrysoloras, a Byzantine scholar, to translate the
text into Latin. Very few scholars, let alone other literate persons in
Western Europe were familiar with the Greek language at this time, therefore
this translation was a great stimulus to "popularizing" Ptolemy.
When Chrysoloras was unable to complete the translation, it was finished
by one of his students, Jacobus Angelus of Scarparia, between 1406 and 1410.
This oldest Latin translation of Ptolemy's Geographia (confusingly
and arbitrarily titled Cosmographia by Angelus) was at first disseminated
in numerous, often splendidly decorated manuscript copies. This was a time
of the rekindling of worldly interest and curiosity. Corrected and amended
by a succession of editors, this version also formed the basis upon which
all of the editions of the 15th century are built.
Again, the original manuscript of Angelus' translation and the first maps
of Ptolemy in the Latin language have not survived, but a manuscript copy,
dated 1427, prepared under the direction of Cardinal Fillastre, can be found
in the library at Nancy, France (thus known as the Nancy Codex ).
In manuscript form, four other cartographers are significant in editing
and influencing the evolution of Ptolemy's atlas. These include P. del Massajo
(1448 -1472), a Florentine cartographer who is credited with introducing
the practice of adding 'modern' or contemporary maps to the Ptolemaic map
selection of twenty-six; Nicholaus Gemmanus [Nicolas Donis], 1464 - 1471
who claimed four 'improvements' for his versions: smaller, more convenient
size maps; employment of a new projection - the trapezoidal; the correction
of the outlines of various countries; and the addition of new maps (his
manuscript maps were the basis for the Bologna edition of 1477 and the Rome
edition of 1478); and Francesco Berlinghieri and Henricus Martellus, both
about 1480.
After the discovery of copper-plate and wood-engraving, Ptolemy's atlas
became one of the first great works for the reproduction of which these
arts were employed. Curiously enough it was first printed at Vincenza in
1475 (the date printed of 1462 is in error) without maps ! In all,
seven editions were printed in the 15th century, of which six were provided
with large maps in folio, and thiry-three in the following century (as elected
list taken from Tooley accompanies this monograph). The demand for knowledge
of the progress of modern geographical discovery, plus the immortal reputation
acquired by the name Ptolemy, became so great that during the next 250 years
the Geographia, in its constantly improved/expanded form, still continued
to be the standard work on the subject, so much so that upwards of 50 editions
or collateral works appeared before 1730.
REFERENCES:
*Bagrow, L., History of Cartography, pp. 33 - 36.
*Brown, L., The Story of Maps, pp. 58 - 80.
*Crone, G.R., Maps and Their Makers, pp. 65 - 73.
*Dilke, O.A.W., Greek and Roman Maps, pp. 27, 35, 71-86,16~166,170.
*Fite & Freemen, A Book of Old Maps. . ., pp. 1- 4.
*Nordenskiöld, A.E., Facsimile Atlas, pp. 1 - 29.
Stevens,E., Ptolemy's Geography
*Tooley, R.V., Maps and Mapmakers, pp. 6 - 7.
*Woodward, D., Art & Cartography, pp. 13, 35, Figures 1.2, 1.18, Plate
16
*illustrated
SLIDES: