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[326] or 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,[328] the 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,[329] at the mouth of the Phasis,[330] the whole of the coast of Themiscyra,[331] named the plain of the Amazons, near the mouths of the Thermodon[332] and Iris,[333] and the greater part of Sidene.[334] It is the same with other rivers, they all resemble the Nile in forming an alluvial deposit