Strabo, Geography (English) (XML Header) [genre: prose] [word count] [Str.].
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However, so nice a fellow is Eratosthenes, that though

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he professes himself a mathematician, [Note] he rejects entirely the dictum of Archimedes, who, in his work On Bodies in Suspension, says that all liquids when left at rest assume a spherical form, having a centre of gravity similar to that of the earth. A dictum which is acknowledged by all who have the slightest pretensions to mathematical sagacity. He says that the Mediterranean, which, according to his own description, is one entire sea, has not the same level even at points quite close to each other; and offers us the authority of engineers for this piece of folly, notwithstanding the affirmation of mathematicians that engineering is itself only one division of the mathematics. He tells us that Demetrius [Note] intended to cut through the Isthmus of Corinth, to open a passage for his fleet, but was prevented by his engineers, who, having taken measurements, reported that the level of the sea at the Gulf of Corinth was higher than at Cenchrea, [Note] so that if he cut through the isthmus, not only the coasts near ægina, but even ægina itself, with the neighbouring islands, would be laid completely under water, while the passage would prove of little value. According to Eratosthenes, it is this which occasions the current in straits, especially the current in the Strait of Sicily, [Note] where effects similar to the flow and ebb of the tide are remarked. The current there changes twice in the course of a day and night, like as in that period the tides of the sea flow and ebb twice. In the Tyrrhenian sea [Note] the current which is called descendent, and which runs towards the sea of Sicily, as if it followed an inclined plane, corresponds to the flow of the tide in the ocean. We may remark, that this current corresponds to the flow both in the time of its commencement and cessation. For it commences at the rising and setting of the moon, and recedes when that satellite attains its meridian, whether above [in the zenith] or below the earth [in the nadir]. In the same way occurs the opposite or ascending current, as it is called. It corresponds to

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the ebb of the ocean, and commences as soon as the moon has reached either zenith or nadir, and ceases the moment she reaches the point of her rising or setting. [So far Eratosthenes.] 1.3.12

The nature of the ebb and flow has been sufficiently treated of by Posidonius and Athenodorus. Concerning the flux and reflux of the currents, which also may be explained by physics, it will suffice our present purpose to observe, that in the various straits these do not resemble each other, but each strait has its own peculiar current. Were they to resemble each other,. the current at the Strait of Sicily [Note] would not change merely twice during the day, (as Eratosthenes himself tells us it does,) and at Chalcis seven times; [Note] nor again that of Constantinople, which does not change at all, but runs always in one direction from the Euxine to the Propontis, and, as Hipparchus tells us, sometimes ceases altogether. However, if they did all depend on one cause, it would not be that which Eratosthenes has assigned, namely, that the various seas have different levels. The kind of inequality he supposes would not even be found in rivers only for the cataracts; and where these cataracts occur, they occasion no ebbing, but have one continued downward flow, which is caused by the inclination both of the flow and the surface; and therefore though they have no flux or reflux they do not remain still, on account of a principle of flowing which is inherent in them; at the same time they cannot be on the same level, but one must be higher and one lower than another. But who ever imagined the surface of the ocean to be on a slope, especially those who follow a system which supposes the four bodies we call elementary, to be spherical. [Note] For water is not like the earth, which being of a solid nature is capable of permanent depressions and risings, but by its force of gravity spreads equally over the earth,

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and assumes that kind of level which Archimedes has assigned it. 1.3.13

To what we cited before concerning the temple of Ammon and Egypt, Eratosthenes adds, that to judge from appearances, Mount Casius [Note] was formerly covered by sea, and the whole district now known as Gerra lay under shoal water touching the bay of the Erythræan Sea, [Note] but was left dry on the union [Note] of the [Mediterranean] Sea [with the ocean]. A certain amphibology lurks here under this description of the district lying under shoal water and touching the bay of the Erythræan Sea; for to touch [Note] both means to be close to, and also to be in actual contact with, so that when applied to water it would signify that one flows into the other. I understand him to mean, that so long as the strait by the Pillars of Hercules remained closed, these marshes covered with shoal- water extended as far as the Arabian Gulf, but on that passage being forced open, the Mediterranean, discharging itself by the strait, became lower, and the land was left dry.

On the other hand, Hipparchus understands by the term touching, that the Mediterranean, being over-full, flowed into the Erythræan Sea, and he inquires how it could happen, that as the Mediterranean flowed out by this new vent at the Pillars of Hercules, the Erythræan Sea, which was all one with it, did not flow away too, and thus become lower, but has always retained the same level? and since Eratosthenes supposes the whole exterior sea to be confluent, it follows that the Western Ocean [Note] and the Erythræan Sea are all one; and thus [remarks Hipparchus] as a necessary consequence, the sea beyond the Pillars of Hercules, the Erythræan Sea, and that also which is confluent with it, [Note] have all the same level.

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14. But, Eratosthenes would reply, I never said that, in con- sequence of the repletion of the Mediterranean, it actually flowed into the Erythræan Sea, but only that it approached very near thereto: besides, it does not follow, that in one and the self-same sea, the level of its surface must be all the same; to instance the Mediterranean itself, no one, surely, will say it is of the same height at Lechæum [Note] and at Cenchrea. [Note] This answer Hipparchus anticipated in his Critique; and being aware of the opinion of Eratosthenes, was justified in attacking his arguments. But he ought not to have taken it for granted, that when Eratosthenes said the exterior sea was all one, he necessarily implied that its level was every where the same.

Strabo, Geography (English) (XML Header) [genre: prose] [word count] [Str.].
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