17. If the followers of Deimachus add to the 30,000 stadia the distance to Taprobane and the boundaries of the torrid zone, which cannot be reckoned less than 4000 stadia,[523] they will then remove Bactria and Aria from their actual localities and place them 34,000 stadia from the torrid zone, a distance equal to that which Hipparchus states to be between the equator and [the mouth of] the Dnieper, and the two countries will therefore be removed 8800 stadia north of [the mouth of] the Dnieper and Keltica; for there are reckoned to be 8800 stadia from the equator to the parallel of latitude which separates the temperate from the torrid zone and which crosses the Cinnamon Country.[524] We have proved that the regions not more than 5000 stadia north of Keltica, as far as Ierne,[525] are scarcely habitable, but their reasoning leads to the conclusion that there is another circle fitted for the habitation of man, although 3800 stadia north of Ierne.[526] And that Bactra is still farther north than the mouth of the Caspian or Hyrcanian Sea, which is distant about 6000 stadia from the recess of the Caspian and the mountains of Armenia and Media, and which appears to be the most northerly point of the whole coast as far as India, with a sea navigable to India all the way, as Patrocles, who had the government of these regions, affirms. Now Bactriana stretches 1000 stadia farther north. Beyond this the Scythians occupy a much larger territory, bounded by the Northern Ocean: here they dwell, though to be sure theirs is a nomade life. But we ask how they could exist here at all, supposing even Bactra to be beyond the limits of the habitable globe. The distance from the Caucasus to the Northern Sea through Bactra would be rather more than 4000 stadia.[527] This being added to the number[528] of stadia north of Ierne[529] above-mentioned, will give us the whole amount of uninhabitable land from Ierne northward 7800 stadia, and even omitting the 4000 stadia altogether, those parts of Bactriana next the Caucasus will still be 3800 stadia farther north than Ierne, and 8800 farther north than Keltica,[530] and [the mouth] of the Dnieper.
18. Hipparchus narrates that at the Dnieper and [the north of] Keltica, during the whole of the summer nights there is one continued twilight from sunset to sunrise, but at the winter solstice the sun never rises more than nine cubits above the horizon.[531] He adds that this phenomenon is yet more remarkable in regions 6300[532] stadia north of Marseilles, (these regions he supposes to be peopled by Kelts, but I believe are inhabited by Britons, and 2500 stadia north of Keltica,) where the sun at the winter solstice[533] rises only six cubits above the horizon. That at 9100[534] stadia north of Marseilles it only rises four cubits, and not so much as three in the countries beyond, and which I consider much farther north than Ierne.[535] However, Hipparchus, on the authority of Pytheas, places them south of Britain, and says that the longest day there consists only of 19 hours;[536] while in countries where the sun rises but four cubits above the horizon, and which are situated 9100[537] stadia north of Marseilles, the day has 18 hours. Consequently [according to his hypothesis] the most southerly parts of Britain must be north of these regions. They must therefore be under the same parallel, or almost the same, as the parts of Bactriana next to the Caucasus, which I have shown are, according to the followers of Deimachus, 3800 stadia farther north than Ierne.[538] Now if we add this to the number between Marseilles and Ierne, we shall get 12,500 stadia. But who ever made known to us that, in those parts, I mean, in the vicinity of Bactra, this was the duration of the longest day, or the height which the sun attains in the meridian at the winter solstice? All these things are patent to the eyes of every man, and require no mathematical investigation; therefore they certainly would have been mentioned by numerous writers both amongst the ancients who have left us histories of Persia, and by the later writers too, who have carried them down to our own time. How, too, would their fertility, which I have described above, harmonize with such a latitude? The facts here advanced are sufficient to give an idea of the learned manner in which Hipparchus attempts to controvert the reasoning of Eratosthenes by mere petitiones principii.
19. Again, Eratosthenes wished to show the ignorance of Deimachus, and his want of information concerning such matters, as proved by his assertion that India lies between the autumnal equinox[539] and winter tropic.[540] Also in his blaming Megasthenes, where he says that in the southern parts of India the Greater and Lesser Bear are seen to set, and the shadows to fall both ways; assuring us that such is not the case in India.[541] These assertions, says Eratosthenes, arise from the ignorance of Deimachus. For it is nothing else than ignorance to suppose that the autumnal equinox is not equally distant from the tropics with the vernal; since in both equinoxes the sun rises at the same point, and performs a similar revolution. Further, [he continues,] the distance from the terrestrial tropic to the equator, between which, according to Deimachus himself, India is situated, has been proved by measurement to be much less than 20,000 stadia, consequently his own statements prove that my assertion is correct, and not his. For supposing India to be twenty or thirty thousand stadia [in breadth] it could not be contained in the given space, but if my estimate be taken it is simple enough. It is another evidence of his want of information, to say that the two Bears are not seen to set, or the shadows to fall both ways, in any part of India, since 5000 stadia south of Alexandria[542] both of these phenomena are observable. Thus reasons Eratosthenes; whom Hipparchus again criticises in the same mistaken way. First he substitutes [in the text of Deimachus] the summer in place of the winter tropic; then he says that the evidence of a man ignorant of astronomy ought not to be received in a mathematical question; as if Eratosthenes in the main had actually been guided by the authority of Deimachus. Could he not see that Eratosthenes had followed the general custom in regard to idle reasoners, one means of refuting whom is to show that their arguments, whatever they may be, go only to confirm our views.
20. It is by assuming as a fact that the southern extremity of India is under the same parallel as Meroe, a thing affirmed and believed by most writers, that we shall be best able to show the absurdities of the system of Hipparchus. In the first book of his Commentaries he does not object to this hypothesis, but in the second book he no longer admits it; we must examine his reasons for this. He says, “when two countries are situated under the same parallel, but separated by a great distance, you cannot be certain that they are exactly under the same parallel, unless the climata[543] of both the places are found to be similar. Now Philo, in his account of a voyage by sea to Ethiopia, has given us the clima of Meroe. He says that at that place the sun is vertical forty-five days before the summer solstice,[544] he also informs us of the proportion of shadow thrown by the gnomon both at the equinoxes and solstices. Eratosthenes agrees almost exactly with Philo. But not a single writer, not even Eratosthenes, has informed us of the clima of India; but if it is the case, as many are inclined to believe on the authority of Nearchus,[545] that the two Bears are seen to set in that country, then certainly Meroe and the southern extremity of India cannot be under the same parallel.”[546] [Such is the reasoning of Hipparchus, but we reply,] If Eratosthenes confirms the statement of those authors who tell us that in India the two Bears are observed to set, how can it be said that not a single person, not even Eratosthenes, has informed us of any thing concerning the clima of India? This is itself information on that point. If, however, he has not confirmed this statement, let him be exonerated from the error. Certain it is he never did confirm the statement. Only when Deimachus affirmed that there was no place in India from which the two Bears might be seen to set, or the shadows fall both ways, as Megasthenes had asserted, Eratosthenes thereupon taxed him with ignorance, regarding as absolutely false this two-fold assertion, one half of which, namely, that concerning the shadows not falling both ways, Hipparchus himself acknowledged to be false; for if the southern extremity of India were not under the same parallel as Meroe, still Hipparchus appears to have considered it south of Syene.
21. In the instances which follow, Hipparchus, treating of these subjects, either asserts things similar to those which we have already refuted, or takes for granted matters which are not so, or draws improper sequences. For instance, from the computation [of Eratosthenes] that the distance from Babylon to Thapsacus[547] is 4800 stadia, and thence northward to the mountains of Armenia[548] 2100 stadia more, it does not follow that, starting from the meridian of that city, the distance to the northern mountains is above 6000 stadia. Besides, Eratosthenes never says that the distance from Thapsacus to these mountains is 2100 stadia, but that a part thereof has never yet been measured; so that this argument [of Hipparchus], founded on a false hypothesis, amounts to nothing. Nor did Eratosthenes ever assert that Thapsacus lies more than 4500 stadia north of Babylon.
22. Again, Hipparchus, ever anxious to defend the [accuracy of the] ancient charts, instead of fairly stating the words of Eratosthenes concerning his third section of the habitable earth, wilfully makes him the author of an assertion easy of disproof. For Eratosthenes, following the opinion we before mentioned, that a line drawn from the Pillars of Hercules across the Mediterranean, and the length of the Taurus, would run due west and east,[549] divides, by means of this line, the habitable earth into two portions, which he calls the northern and southern divisions; each of these he again essays to subdivide into as many smaller partitions as practicable, which he denominates sections.[550] He makes India the first section of the southern part, and Ariana[551] the second; these two countries possessing a good outline, he has been able not only to give us an accurate statement of their length and breadth, but an almost geometrically exact description of their figure. He tells us that the form of India is rhomboidal, being washed on two of its sides by the southern and eastern oceans [respectively], which do not deeply indent its shores. The two remaining sides are contained by its mountains and the river [Indus], so that it presents a kind of rectilinear figure.[552] As to Ariana, he considered three of its sides well fitted to form a parallelogram; but of the western side he could give no regular definition, as it was inhabited by various nations; nevertheless he attempts an idea of it by a line drawn from the Caspian Gates[553] to the limits of Carmania, which border on the Persian Gulf. This side he calls western, and that next the Indus eastern, but he does not tell us they are parallel to each other; neither does he say this of the other sides, one bounded by the mountains, and the other by the sea; he simply calls them north and south.
23. Having in this manner but imperfectly traced the outlines of his second section, the third section, for various reasons, is still less exact. The first cause has been already explained, viz. that the line from the Caspian Gates to Carmania is not clearly defined, as the side of the section is common both to the third and second sections. Secondly, on account of the Persian Gulf interrupting the continuity of the southern side, as he himself tells us, he has been obliged to take the measured road running through Susa and Persepolis to the boundaries of Carmania and Persia, and suppose it straight.[554] This road, which he calls the southern side, is a little more than 9000 stadia. He does not, however, tell us, that it runs parallel to the northern side. It is also clear that the Euphrates, which he makes the western boundary, is any thing but a straight line. On leaving the mountains it flows south, but soon shifts its course to the east; it then again pursues a southerly direction till it reaches the sea. In fact, Eratosthenes himself acknowledges the indirect course of this river, when he compares the shape of Mesopotamia, which is formed by the junction of the Tigris and Euphrates, to the cushion on a rower’s bench. The western side bounded by the Euphrates is not entirely measured; for he tells us that he does not know the extent of the portion between Armenia and the northern mountains,[555] as it has not been measured. By reason of these hinderances he states that he has been only able to give a very superficial view of the third section, and that his estimate of the distances is borrowed from various Itineraries, some of them, according to his own description, anonymous. Hipparchus therefore must be considered guilty of unfairness, for criticising with geometrical precision a work of this general nature. We ought rather to be grateful to a person who gives us any description at all of the character of such [unknown] places. But when he urges his geometrical objections not against any real statement of Eratosthenes, but merely against imaginary hypotheses of his own creation, he shows too plainly the contradictory bent of his mind.
24. It is in this general kind of description of the third section that Eratosthenes supposes 10,000 stadia from the Caspian Gates to the Euphrates. This he again divides according to former admeasurements which he found preserved. Starting from the point where the Euphrates passes near to Thapsacus, he computes from thence to the place where Alexander crossed the Tigris 2400 stadia. The route thence through Gaugamela,[556] the Lycus,[557] Arbela,[558] and Ecbatana,[559] whither Darius fled from Gaugamela to the Caspian Gates, makes up the 10,000 stadia, which is only 300 stadia too much. Such is the measure of the northern side given by Eratosthenes, which he could not have supposed to be parallel to the mountains, nor yet to the line drawn from the Pillars of Hercules through Athens and Rhodes. For Thapsacus is far removed from the mountains, and the route from Thapsacus to the Caspian Gates only falls in with the mountains at that point.[560] Such is the boundary on the northern side.
25. Thus, says Eratosthenes, we have given you a description of the northern side; as for the southern, we cannot take its measure along the sea, on account of the Persian Gulf, which intercepts [its continuity], but from Babylon through Susa and Persepolis to the confines of Persia and Carmania there are 9200 stadia. This he calls the southern side, but he does not say it is parallel to the northern. The difference of length between the northern and southern sides is caused, he tells us, by the Euphrates, which after running south some distance shifts its course almost due east.
26. Of the two remaining sides, he describes the western first, but whether we are to regard it as one single straight line, or two, seems to be undecided. He says,—From Thapsacus to Babylon, following the course of the Euphrates, there are 4800 stadia; from thence to the mouth of the Euphrates[561] and the city of Teredon, 3000[562] more; from Thapsacus northward to the Gates of Armenia, having been measured, is stated to be 1100 stadia, but the distance through Gordyæa and Armenia, not having yet been measured, is not given. The eastern side, which stretches lengthwise through Persia from the Red Sea towards Media and the north, does not appear to be less than 8000 stadia, and measured from certain headlands above 9000, the rest of the distance through Parætacena and Media to the Caspian Gates being 3000 stadia. The rivers Tigris and Euphrates flowing from Armenia towards the south, after having passed the Gordyæan mountains, and having formed a great circle which embraces the vast country of Mesopotamia, turn towards the rising of the sun in winter and the south, particularly the Euphrates, which, continually approaching nearer and nearer to the Tigris, passes by the rampart of Semiramis,[563] and at about 200 stadia from the village of Opis,[564] thence it flows through Babylon, and so discharges itself into the Persian Gulf. Thus the figure of Mesopotamia and Babylon resembles the cushion of a rower’s bench.—Such are the words of Eratosthenes.