A General History and Collection of Voyages and Travels - Volume 18 / Historical Sketch of the Progress of Discovery, Navigation, and / Commerce, from the Earliest Records to the Beginning of the Nineteenth / Century, By William Stevenson

by Robert Kerr; William Stevenson

One of the most important and complete surveys of the Roman empire (the idea of which, as has been already stated, was first formed by Julius Cæsar) was begun and finished in the reign of Antoninus, and is well known under the appellation of his Itinerary. It has, indeed, been objected to this date of the Itinerary, that it contains places which were not known in the time of Antonine, and names of places which they did not bear till after his reign; thus mention is made of the province of Arcadia in Egypt, and of Honorius in Pontus, so styled in honor of the sons of the emperor Theodosius. But the fact seems to be that alterations and additions were made to the Itinerary, and that occasionally, or perhaps under each subsequent emperor, new editions of it were published. From the maritime part of this Itinerary of Antoninus we derive a clear idea of the timidity or want of skill and enterprise of the Mediterranean seamen in their commercial voyages. All the ports which it was prudent or necessary, for the safety of the voyage, to touch at, in sailing from Achaia to Africa are enumerated; and of these there are no fewer than twenty, some of them at the heads of bays on the coasts of Greece, Epirus, and Italy, and within the Straits of Sicily as far as Messina. Their course was then to be directed along the east and south coasts of Sicily to the west point of it; from an island off this point they took their departure for the coast of Africa, a distance of about ninety miles.

These Itineraries undoubtedly were drawn up in as accurate a manner as possible; but till the time of Ptolemy they were of little service to geography or commerce, as, for a private individual to have one in his possession was deemed a crime little short of high treason. Geography as a science, therefore, had hitherto made little advances; indeed the discovery and example of Hipparchus, of reducing it to astronomical basis, seems to have been forgotten or neglected till the middle of the second century. The first after him, who attempted to fix geography on the base of science was Marinus, of Tyre, who lived a short time before Ptolemy; of his work we have only extracts given by this geographer. He divided the terms latitude and longitude, which, as we have already stated, were introduced by Artemidorus (A.C. 104) into degrees, and these degrees into their parts, though this improvement was not reduced generally to practice before Ptolemy, for we are informed by him, that Marinus had the latitude of some places and the longitude of others, but scarcely one position where he could ascertain both.

With regard to the extent of Marinus' geographical knowledge, or the accuracy of his details, we cannot form a fair judgment from the fragments of his works which remain. According to Ptolemy, he had examined the history of preceding ages, and all the information that had been collected in his own time, comparing and rectifying them as he proceeded in his own account.

It will be recollected that the Periplus of the Erythrean Sea did not trace the African coast lower down than Rhapta; but Marinus mentions Prasum, which, according to that hypothesis, which fixes it in the lowest southern latitude, must have been seven degrees to the south of Rhapta. So far, therefore, the knowlege of the ancients, in the time of Marinus, respecting the east coast of Africa extended; but, as neither he nor Ptolemy mentions a single place between Rhapta and Prasum, it is probable that the latter was not frequently or regularly visited for the purposes of trade, but that commercial voyages were still confined to the limit of Rhapta. We have just stated that Prasum, according to the most moderate hypothesis, must be fixed seven degrees to the south of Rhapta. Marinus, however, fixes it either in thirty-five degrees south, or under the tropic of Capricorn. He was led into this and similar errors by assigning too great a number of stadia to the degree. Ptolemy endeavours to correct him, and places Prasum in latitude 15, 30 south; it is remarkable that the Prasum of Ptolemy is precisely at Mosambique, the last of the Arabian settlements in the following ages, and the Prasum of Marinus, if under the tropic of Capricorn, is the limit of the knowledge of the Arabians on this coast of Africa.

Marinus, as quoted by Ptolemy, affirms that he was in possession of the journals of two expeditions under the command of Septimus Flaccus and Julius Maternus: the former of these officers set off from Cyrene, and the latter from Leptis; and, according to Marinus, they penetrated through the interior of Africa to the southward of the Equator, as far as a nation they styled Agesymba. The error of Marinus with respect to the valuation of the stadium, has led him to fix this nation in twenty-four degrees south latitude; if allowance, however, be made for his error, the Agesymba will still be placed under the Equator,--a great distance for a land expedition to have readied in the interior of Africa. Flaccus reported that the Ethiopians of Agesymba, were three months journeying to the south of the Garamantes, and the latter were 5400 of the stadia of Marinus, distant from Cyrene. According to the journal of Maternus, when the king of the Garamantes set off to attack the people of Agesymba, he marched four months to the south.

There are also some notices in Marinus of voyages performed along the coast of Africa, between India and Africa, and along part of the coast of India; he particularly mentions one Theophilus who frequented the coast of Azania, and who was carried by a south-west wind from Rhapta to Aromata in twenty days; and Diogenes, one of the traders to India, who on his return after he had come in sight of Aromata, was caught by the north-east monsoon, and carried down the coast during twenty-five days, till he reached the lakes from which the Nile issues. Marinus also mentions a Diogenes Samius, who describes the course held by vessels from the Indus to the coast of Cambay, and from Arabia to the coast of Africa. According to him, in the former voyage they sailed with the Bull in the middle of the heavens, and the Pleiades in the middle of the main yard; in the latter voyage, they sailed to the south, and by the star Canobus.

We now arrive at the name of Ptolemy, certainly the most celebrated geographer of antiquity. He was a native of Alexandria, and flourished in the reign of the emperor Marcus Antoninus. In the application of astronomy to geography, he followed Hipparchus principally, and he seems from his residence at Alexandria to have derived much information through the merchants and navigators of that city, as well as from its magnificent and valuable library. His great work, as it has reached us, consists almost entirely of an elementary picture of the earth, (if it may be so called,) in which its figure and size, and the position of places are determined. There is only a short notice of the division of countries, and it is very seldom that any historical notice is added. To this outline, it is supposed that Ptolemy had added a detailed account of the countries then known, which is lost.

His geography, such as we have described it, consists of eight books, and is certainly much more scientific than any which had been previously written on this science. In it there appears, for the first time, an application of geometrical principles to the construction of maps: the different projections of the sphere, and a distribution of the several places on the earth, according to their latitude and longitude. Geography was thus established on its proper principles, and intimately connected with astronomical observations and mathematical science. The utility and merit of Ptolemy's work seems to have been understood and acknowledged soon after it appeared. Agathemidorus, who lived not long after him, praises him for having reduced geography to a regular system; and adds, that he treats of every thing relating to it, not carelessly, or merely according to the ideas of his own, but to what had been delivered by more ancient authors, adopting from them whatever he found consonant to truth. Agathodæmon, an artist of Alexandria, observing the request in which his work was held, prepared a set of maps to illustrate it, in which all the places mentioned in it were laid down, with the latitudes and longitudes he assigned them. The reputation of his geography remained unshaken and undiminished during the middle ages, both in Arabia and Europe; and even now, the scientific language which he first employed, is constantly used, and the position of places ascertained by specifying their latitude and longitude.

It was not to be expected, however, that Ptolemy could accurately fix the longitude and latitude of places in the remoter parts of the then known world; his latitudes and longitudes are accordingly frequently erroneous, but especially the latter. This arose partly from his taking five hundred stadia for a degree of a great circle, and partly from the vague method of calculating distances, by the estimate of travellers and merchants, and the number of days employed in their journies by land, and voyages by sea. As he took seven hundred stadia for a degree of latitude, his errors in latitude are not so important; and though the latitude he assigns to particular places is incorrect, yet the length of the globe, according to him, or the distance from the extreme points north and south, then known, is not far from the truth. Thus the latitude of Thule, according to Ptolemy, is 64 degrees north, and the parallel through the cinnamon country 16° 24' south, that is, 80° 24' on the whole, a difference from the truth of not more than six or seven degrees. It is remarked by D'Anville, and Dr. Vincent coincides in the justice of the remark, that the grandest mistake in the geography of Ptolemy has led to the greatest discovery of modern times. Strabo had affirmed, that nothing obstructed the passage from Spain to India by a westerly course, but the immensity of the Atlantic ocean; but, according to Ptolemy's errors in longitude, this ocean was lessened by sixty degrees; and as all the Portuguese navigators were acquainted with his work, as soon as it was resolved to attempt a passage to India, the difficulty was, in their idea, lessened by sixty degrees; and when Columbus sailed from Spain, he calculated on sixty degrees less than the real distance from that country to India. Thus, to repeat the observation of D'Anville, the greatest of his errors proved eventually the efficient cause of the greatest discovery of the moderns.

Beside the peculiar merit of Ptolemy, which was perceived and acknowledged as soon as his work appeared, he possesses another excellence, which, as far as we know, was first pointed out and dwelt upon by Dr. Vincent. According to him, Ptolemy, in his description of India, serves as the point of connection between the Macedonian orthography and the Sanscrit, dispersing light on both sides, and showing himself like a luminary in the centre. He seems indeed to have obtained the native appellations of the places in India, in a wonderful manner; and thus, by recording names which cannot be mistaken, he affords the means of ascertaining the country, even though he gives no particulars regarding it. We have applied this remark to India exclusively, but it might be extended to almost all the names of places that occur in Ptolemy, though, as respects India, his obtaining the native appellations is more striking and useful.