Page:EB1911 - Volume 22.djvu/641

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geography]
625
PTOLEMY

graduation. Thus while Marinus calculated 24,800 stadia as the length of the Mediterranean from the Straits to the Gulf of Issus, this was stated by Ptolemy at 62°, or about 20° too much. Even after correcting the error due to his computation of 500 stadia to a degree, there remains an excess of nearly 500 geographical miles.

Another error which disfigured the eastern portion of Ptolemy’s Mediterranean map was the position of Byzantium, which Ptolemy (misled by Hipparchus) placed in the same latitude with Massilia, thus carrying it up more than 2° above its true position. This pushed the whole Euxine—with whose general form and dimensions he was fairly well acquainted—too far north by the same amount; besides this he enormously exaggerated the extent of the Palus Maeotis (the Sea of Azov), which he also represented as having its direction from south to north; by the combined effect of these two errors he carried up its northern extremity (with the Tanais estuary and city) as high as 54° 30′ (the true south shore of the Baltic). Ptolemy, however, was the first writer of antiquity who showed some relations between the Tanais or Don (usually considered by the ancients as the boundary between Europe and Asia) and the Rha or Volga, which he correctly described as flowing into the Caspian. He was also the first geographer after Alexander to return to the correct view (found in Herodotus and Aristotle) that the Caspian was an inland sea, without communication with the ocean.

As to north Europe, Ptolemy’s views were vague and imperfect. He had indeed more acquaintance with the British Islands than any previous geographer, and showed a remarkable knowledge of certain British coast-lines. But he (1) placed Ireland (Ivernia) farther north than any part of Wales, and (2) twisted round the whole of Scotland, so as to make its length from west to east and to place the northern extremities of Britain and Ireland almost on the same parallel. These errors are probably connected and are naturally accompanied by the placing of Thule, the Orkneys (Orcades) and the Hebrides (Ebudae) indiscriminately on the left or north of Caledonia. Here he was perhaps embarrassed by adopting Marinus' conclusion that Thule lay in 63° N., while regarding it, like earlier geographers, as the northernmost of all lands. Ptolemy also supposed the northern coast of Germany, beyond the Cimbric Chersonese (Denmark), to be the southern shore of the Northern Ocean, with a general direction from west to east. Of the almost wholly landlocked Baltic he was entirely ignorant, as well as of the Scandinavian Peninsula; his Scandia is an island smaller than Corsica, lying in the true position of southern central Sweden. Some way east of the Vistula, Ptolemy, however, makes the Sarmatian coast trend north, to the parallel of Thule; nor did he conceive this as an actual limit, but believed the Unknown Land to extend indefinitely in this direction as also to the north of Asiatic Scythia.

As to the latter region, vague and erroneous as were his views concerning this enormous tract from Sarmatia to China, they show an advance on those of earlier geographers. Ptolemy was the first who had anything like a clear idea of the great north-and-south dividing range of Central Asia (the Pamir and Tian Shan), which he called lmaus, placing it nearly 40° too far east, and making it divide Scythia into two portions (Within Imaus and Beyond Imaus), somewhat corresponding to Russian and Chinese Central Asia. Ptolemy also applies the term Imaus to a section of the backbone range which in his system crosses Asia from west to east. This section lies east of the Indian Caucasus, and forms an angle with the other lmaus running north.

On the southern shores of Asia Ptolemy’s geography is especially faulty, though he shows a greatly increased general knowledge of these regions. For more than a century the commercial relations between western India and Alexandria, the chief eastern emporium of the Roman Empire, had become more important and intimate than ever before. The tract called the Periplus of the Erythraean Sea, about A.D. 80, contains sailing directions for merchants from the Red Sea to the Indus and Malabar, and even indicates that the coast from Barygaza (Baroch) had a general southward direction down to and far beyond Cape Komari (Comorin), which, taken together with its account of the shore-line as far as the Ganges, affords some suggestions at least of a peninsular character for south India. But Ptolemy, following Marinus, not only gives to the Indian coasts, from Indus to Ganges, an undue extension in longitude, but practically denies anything of an Indian peninsula, placing capes Komaria and Kory (his southernmost points in India) only 4° S. of Barygaza, the real interval being over 800 geographical miles, or, according to Ptolemy’s system of graduation, 16° of latitude. This error, distorting the whole appearance of south Asia, is associated with another as great, but of opposite tendency, in regard to Taprobane (in which ancient ideas of Ceylon and Sumatra are confusedly mingled). The size of this was exaggerated by most earlier Greek geographers; but Ptolemy extended it through 15° of latitude and 12° of longitude, so as to make it about fourteen times as large as the reality, and bring down its southern extremity more than 2° south of the equator.

Similar distortions in regions beyond the Ganges, concerning which Ptolemy is our only ancient authority, are less surprising. Between the date of the Periplus and that of Marinus it seems probable that Greek mariners had not only crossed the Gangetic gulf and visited the land on the opposite side, which they called the Golden Chersonese, but pushed considerably farther east, to Cattigara. But these commercial voyagers either brought back inaccurate notions, or Ptolemy’s preconceptions destroyed the value of the new information, for nowhere does he distort the truth more wildly. After passing the Great Gulf, beyond the Golden Chersonese, he makes the coast trend southward, and thus places Cattigara (perhaps one of the south China ports) 8½° south of the equator. In this he was perhaps influenced by his notion of a junction of Asia and Africa in a terra incognita, south of the Indian Ocean.

In regard to West Africa, we may notice that he conceives this coast as running almost due north and south to 10° N., and then (after forming a great bay) as bending away to the unknown southwest. Though the Fortunate Islands were so important to his system as his prime meridian, he was entirely misinformed about them, and extended the group through more than 5° of latitude, so as to bring down the most southerly of them to the real parallel of the Cape Verde Islands.

In regard to the mathematical construction or projection of his maps, not only was Ptolemy greatly in advance of all his predecessors, but his theoretical skill was altogether beyond the nature of the materials to which he applied it. The methods by which he obviated the difficulty of transferring the delineation of different countries from the spherical surface of the globe to the plane surface of an ordinary map differed little from those in use at the present day, and the errors arising from this cause (apart from those produced by his fundamental error of radiation) were really of little consequence compared with the defective character of his information and the want of anything approaching to a survey of the countries delineated. He himself was well aware of his deficiencies in this respect, and, while giving full directions for the scientific construction of a general map, he contents himself, for the special maps of different countries, with the simple method employed by Marinus of drawing the parallels of latitude and meridians of longitude as straight lines, assuming in each case the proportion between the two, as it really stood with respect to some one parallel towards the middle of the map, and neglecting the inclinations of the meridians to one another. Such a course, as he himself repeatedly affirms, will not make any material difference within the limits of each special map.

Ptolemy especially devoted himself to the mathematical branch of his subject, and the arrangement of his work, in which his results are presented in a tabular form, instead of being at once embodied in a map, was undoubtedly designed to enable the student to construct his maps for himself. This purpose it has abundantly served, and there is little doubt that we owe to the peculiar form thus given to his results their transmission in a comparatively perfect condition to the present day. Unfortunately the specious appearance of these results has led to the belief that what was stated in so scientific a form must necessarily be based upon scientific observations. Though Ptolemy himself has distinctly pointed out in his first book the defective nature of his materials, and the true character of the data furnished by his tables, few readers studied this portion of his work, and his statements were generally received with undoubting faith. It is only in modern times that his apparently scientific work has been shown to be in most cases a specious edifice resting upon no adequate foundations.

There can be no doubt that the work of Ptolemy was from the time of its first publication accompanied with maps, which are regularly referred to in the eighth book. But how far those which are now extant represent the original series is a disputed point. In two of the most ancient MSS. it is expressly stated that the maps which accompany them are the work of one Agathodaemon of Alexandria, who “ drew them according to the eight books of Claudius Ptolemy.” This expression might equally apply to the work of a contemporary draughtsman under the eyes of Ptolemy himself, or to that of a skilful geographer at a later period, and nothing is known from any other source concerning this Agathodaemon. The attempt to identify him with a grammarian of the same name who lived in the 5th century is wholly without foundation. But it appears, on the whole, most probable that the maps appended to the MSS. still extant have been transmitted by uninterrupted tradition from the time of Ptolemy.

2. Progress of Geographical Knowledge in Certain Special Regions.—Ptolemy records, after Marinus, the penetration of Roman expeditions to the land of the Ethiopians and to Agisymba, clearly some region of the Sudan beyond the Sahara desert, perhaps the basin of Lake Chad. But while this name was the only recorded result of these expeditions, Ptolemy also gives much other information concerning the interior of North Africa (whence derived we know not) to which nothing similar is found in any earlier writer. Unfortunately this new information was of so crude a character, and is presented in so embarrassing a form, as to perplex rather than assist. Thus Ptolemy’s statements concerning the rivers Gir and Nigir, and the lakes and mountains with which they were connected, have baffled successive generations of interpreters. It may safely be said that they present no resemblance to the real features of the country as now known, and cannot be reconciled with them except by arbitrary conjecture.

As to the Nile, both Greeks and Romans had long endeavoured to discover the sources of this river, and an expedition sent out for that purpose by the emperor Nero had undoubtedly penetrated as far