Strabo - The Geography of Strabo (Vol.1-3)

5. In regard to Strato, however, we must remark that, leaving out of the question the many arguments he has properly stated, some of those which he has brought forward are quite inadmissible. For first he is inaccurate in stating that the beds of the interior and the exterior seas have not the same level, and that the depth of those two seas is different: whereas the cause why the sea is at one time raised, at another depressed, that it inundates certain places and again retreats, is not that the beds have different levels, some higher and some lower, but simply this, that the same beds are at one time raised, at another depressed, causing the sea to rise or subside with them; for having risen they cause an inundation, and when they subside the waters return to their former places. For if it is so, an inundation will of course accompany every sudden increase of the waters of the sea, [as in the spring-tides,] or the periodical swelling of rivers, in the one instance the waters being brought together from distant parts of the ocean, in the other, their volume being increased. But the risings of rivers are not violent and sudden, nor do the tides continue any length of time, nor occur irregularly; nor yet along the coasts of our sea do they cause inundations, nor any where else. Consequently we must seek for an explanation of the cause either in the stratum composing the bed of the sea, or in that which is overflowed; we prefer to look for it in the former, since by reason of its humidity it is more liable to shiftings and sudden changes of position, and we shall find that in these matters the wind is the great agent after all. But, I repeat it, the immediate cause of these phenomena, is not in the fact of one part of the bed of the ocean being higher or lower than another, but in the upheaving or depression of the strata on which the waters rest. Strato’s hypothesis evidently originated in the belief that that which occurs in rivers is also the case in regard to the sea; viz. that there is a flow of water from the higher places. Otherwise he would not have attempted to account for the current he observed at the Strait of Byzantium in the manner he does, attributing it to the bed of the Euxine being higher than that of the Propontis and adjoining ocean, and even attempting to explain the cause thereof: viz. that the bed of the Euxine is filled up and choked by the deposit of the rivers which flow into it; and its waters in consequence driven out into the neighbouring sea. The same theory he would apply in respect to the Mediterranean and Atlantic, alleging that the bed of the former is higher than that of the latter in consequence of the number of rivers which flow into it, and the alluvium they carry along with them. In that case there ought to be a like influx at the Pillars and Calpe, 325as there is at Byzantium. But I waive this objection, as it might be asserted that the influx was the same in both places, but owing to the interference of the ebb and flow of the sea, became imperceptible.

6. I rather make this inquiry:—If there were any reason why, before the outlet was opened at Byzantium, the bed of the Euxine (being deeper than either that of the Propontis 326or of the adjoining sea 327) should not gradually have become more shallow by the deposit of the rivers which flow into it, allowing it formerly either to have been a sea, or merely a vast lake greater than the Palus Mæotis? This proposition being conceded, I would next ask, whether before this the bed of the Euxine would not have been brought to the same level as the Propontis, and in that case, the pressure being counter-poised, the overflowing of the water have been thus avoided; and if after the Euxine had been filled up, the superfluous waters would not naturally have forced a passage and flowed off, and by their commingling and power have caused the Euxine and Propontis to flow into each other, and thus become one sea? no matter, as I said above, whether formerly it were a sea or a lake, though latterly certainly a sea. This also being conceded, they must allow that the present efflux depends neither upon the elevation nor the inclination of the bed, as Strato’s theory would have us consider it.

7. We would apply the same arguments to the whole of the Mediterranean and Atlantic, and account for the efflux of the former, not by any [supposed] difference between the elevation and inclination of its bed and of that of the Atlantic, but attribute it to the number of rivers which empty themselves into it. Since, according to this supposition, it is not incredible that had the whole of the Mediterranean Sea in times past been but a lake filled by the rivers, and having overflowed, it might have broken through the Strait at the Pillars, as through a cataract; and still continuing to swell more and more, the Atlantic in course of time would have become confluent by that channel, and have run into one level, the Mediterranean thus becoming a sea. In fine, the Physician did wrong in comparing the sea to rivers, for the latter are borne down as a descending stream, but the sea always maintains its level. The currents of straits depend upon other causes, not upon the accumulation of earth formed by the alluvial deposit from rivers, filling up the bed of the sea. This accumulation only goes on at the mouths of rivers. Such are what are called the Stethe or Breasts at the mouth of the Ister, 328the desert of the Scythians, and Salmydessus, which are partially occasioned by other winter-torrents as well; witness the sandy, low, and even coast of Colchis, 329at the mouth of the Phasis, 330the whole of the coast of Themiscyra, 331named the plain of the Amazons, near the mouths of the Thermodon 332and Iris, 333and the greater part of Sidene. 334It is the same with other rivers, they all resemble the Nile in forming an alluvial deposit at their mouths, some more, some less than others. Those rivers which carry but little soil with them deposit least, while others, which traverse an extended and soft country, and receive many torrents in their course, deposit the greatest quantity. Such for example is the river Pyramus, 335by which Cilicia has been considerably augmented, and concerning which an oracle has declared, “This shall occur when the wide waters of the Pyramus have enlarged their banks as far as sacred Cyprus.” 336This river becomes navigable from the middle of the plains of Cataonia, and entering Cilicia 337by the defiles of the Taurus, discharges itself into the sea which flows between that country and the island of Cyprus.

8. These river deposits are prevented from advancing further into the sea by the regularity of the ebb and flow, which continually drive them back. For after the manner of living creatures, which go on inhaling and exhaling their breath continually, so the sea in a like way keeps up a constant motion in and out of itself. Any one may observe who stands on the sea-shore when the waves are in motion, the regularity with which they cover, then leave bare, and then again cover up his feet. This agitation of the sea produces a continual movement on its surface, which even when it is most tranquil has considerable force, and so throws all extraneous matters on to the land, and

“Flings forth the salt weed on the shore.” 338

This effect is certainly most considerable when the wind is on the water, but it continues when all is hushed, and even when it blows from land the swell is still carried to the shore against the wind, as if by a peculiar motion of the sea itself. To this the verses refer—

“O’er the rocks that breast the flood

Borne turgid, scatter far the showery spray,” 339

and,

“Loud sounds the roar of waves ejected wide.” 340

9. The wave, as it advances, possesses a kind of power, which some call the purging of the sea, to eject all foreign substances. It is by this force that dead bodies and wrecks are cast on shore. But on retiring it does not possess sufficient power to carry back into the sea either dead bodies, wood, or even the lightest substances, such as cork, which may have been cast out by the waves. And by this means when places next the sea fall down, being undermined by the wave, the earth and the water charged with it are cast back again; and the weight [of the mud] working at the same time in conjunction with the force of the advancing tide, it is the sooner brought to settle at the bottom, instead of being carried out far into the sea. The force of the river current ceases at a very little distance beyond its mouth. Otherwise, supposing the rivers had an uninterrupted flow, by degrees the whole ocean would be filled in, from the beach onwards, by the alluvial deposits. And this would be inevitable even were the Euxine deeper than the sea of Sardinia, than which a deeper sea has never been sounded, measuring, as it does, according to Posidonius, about 1000 fathoms. 341