Narrative and Critical History of America, Vol. 1 (of 8) / Aboriginal America

by Unknown

Plato, who was familiar with the doctrines of the Pythagoreans, adopted their view of the form of the earth, and did much to popularize it among his countrymen.[261] To the generation that succeeded him, the sphericity of the earth was a fact as capable of logical demonstration as a geometrical theorem. Aristotle, in his treatise “On the Heaven,” after detailing the views of those philosophers who regarded the earth as flat, drum-shaped, or cylindrical, gives a formal summary of the grounds which necessitate the assumption of its sphericity, specifying the tendency of all things to seek the centre, the unvarying circularity of the earth’s shadow at eclipses of the moon, and the proportionate change in the altitude of stars resulting from changes in the observer’s latitude. Aristotle made the doctrine orthodox; his successors, Eratosthenes, Hipparchus, and Ptolemy, constituted it an inalienable possession of the race. Greece transmitted it to Rome, Rome impressed it upon barbaric Europe; taught by Pliny, Hyginus, Manilius, expressed in the works of Cicero, Virgil, Ovid, it passed into the school-books of the Middle Ages, whence, reinforced by Arabian lore, it has come down to us.[262]

That the belief ever became in antiquity or in the Middle Ages widely spread among the people is improbable; it did not indeed escape opposition among the educated; writers even of the Augustan age sometimes appear in doubt.[263]

The sphericity of the earth once comprehended, there follow certain corollaries which the Greeks were not slow to perceive. Plato, indeed, who likened the earth to a ball covered with party-colored strips of leather, gives no estimate of its size, although the description of the world in the Phaedo seems to imply immense magnitude;[264] but Aristotle states that mathematicians of his day estimated the circumference at 400,000 stadia,[265] and Archimedes puts the common reckoning at somewhat less than 300,000 stadia.[266] How these figures were obtained we are not informed. The first measurement of the earth which rests on a known method was that made about the middle of the third century b.c., by Eratosthenes, the librarian at Alexandria, who, by comparing the estimated linear distance between Syene, under the tropic, and Alexandria with their angular distance, as deduced from observations on the shadow of the gnomon at Alexandria, concluded that the circumference of the earth was 250,000 or 252,000 stadia.[267] This result, owing to an uncertainty as to the exact length of the stade used in the computation, cannot be interpreted with confidence, but if we assume that it was in truth about twelve per cent. too large, we shall probably not be far out of the way.[268] Hipparchus, in many matters the opponent of Eratosthenes, adopted his conclusion on this point, and was followed by Strabo,[269] by Pliny, who regarded the attempt as somewhat over-bold, but so cleverly argued that it could not be disregarded,[270] and by many others.

Fortunately, as it resulted, this overestimate was not allowed to stand uncontested. Posidonius of Rhodes (b.c. 135-51), by an independent calculation based upon the difference in altitude of Canopus at Rhodes and at Alexandria, reached a result which is reported by Cleomedes as 240,000, and by Strabo as 180,000 stadia.[271] The final judgment of Posidonius apparently approved the smaller number; it hit, at all events, the fancy of the time, and was adopted by Marinus of Tyre and by Ptolemy,[272] whose authority imposed it upon the Middle Ages. Accepting it as an independent estimate, it follows that Posidonius allowed but 500 stadia to a degree, instead of 700, thus representing the earth as about 28 per cent. smaller than did Eratosthenes.[273]

To the earliest writers the known lands constituted the earth; they were girdled, indeed, by the river Oceanus, but that was a narrow stream whose further bank lay in fable-land.[274] The promulgation of the theory of the sphericity of the earth and the approximate determination of its size drew attention afresh to the problem of the distribution of land and water upon its surface, and materially modified the earlier conception. The increase of geographical knowledge along lines of trade, conquest, and colonization had greatly extended the bounds of the known world since Homer’s day, but it was still evident that by far the larger portion of the earth, taking the smallest estimate of its size, was still undiscovered,—a fair field for speculation and fantasy.[275]

We can trace two schools of thought in respect to the configuration of this unknown region, both represented in the primitive conception of the earth, and both conditioned by a more fundamental postulate. It was a near thought, if the earth was a sphere, to transfer to it the systems of circles which had already been applied to the heavens. The suggestion is attributed to Thales, to Pythagoras, and to Parmenides; and it is certain that the earth was very early conceived as divided by the polar and solstitial circles into five zones, whereof two only, the temperate in either sphere, so the Greeks believed, were capable of supporting life; of the others, the polar were uninhabitable from intense cold, as was the torrid from its parching heat. This theory, which excluded from knowledge the whole southern hemisphere and a large portion of the northern, was approved by Aristotle and the Homeric school of geographers, and by the minor physicists. As knowledge grew, its truth was doubted. Polybius wrote a monograph, maintaining that the middle portion of the torrid zone had a temperate climate, and his view was adopted by Posidonius and Geminus, if not by Eratosthenes. Marinus and Ptolemy, who knew that commerce was carried on along the east coast of Africa far below the equator, cannot have fallen into the ancient error, but the error long persisted; it was always in favor with the compilers, and thus perhaps obtained that currency in Rome which enabled it to exert a restrictive and pernicious check upon maritime endeavor deep into the Middle Ages.[276]

Upon the question of the distribution of land and water, unanimity no longer prevailed. By some it was maintained that there was one ocean, confluent over the whole globe, so that the body of known lands, that so-called continent, was in truth an island, and whatever other inhabitable regions might exist were in like manner surrounded and so separated by vast expanses of untraversed waves. Such was the view, scarcely more than a survival of the ocean-river of the poets deprived of its further bank by the assumption of the sphericity of the earth, held by Aristotle,[277] Crates of Mallus, Strabo, Pliny, and many others. If this be called the oceanic theory, we may speak of its opposite as the continental: according to this view, the existing land so far exceeded the water in extent that it formed in truth the continent, holding the seas quite separate within its hollows. The origin of the theory is obscure, even though we recall that Homer’s ocean was itself contained. It was strikingly presented by Plato in the Phaedo, and is implied in the Atlantis myth; it may be recalled, too, that Herodotus, often depicted as a monster of credulity, had broken the bondage of the ocean-river, because he could not satisfy himself of the existence of the ocean in the east or north; and while reluctantly admitting that Africa was surrounded by water, considered Gaul to extend indefinitely westward.[278] Hipparchus revived the doctrine, teaching that Africa divided the Indian Ocean from the Atlantic in the south, so that these seas lay in separate basins. The existence of an equatorial branch of the ocean, a favorite dogma of the other school, was also denied by Polybius, Posidonius, and Geminus.[279]

The reports of traders and explorers led Marinus to a like conclusion; both he and Ptolemy, misinterpreting their information, believed that the eastern coast of Asia ran south instead of north, and they united it with the eastern trend of Africa, supposing at the same time that the two continents met also in the west.[280] The continental theory, despite its famous disciples, made no headway at Rome, and was consequently hardly known to the Middle Ages before its falsity was proved by the circumnavigation of Africa.[281]