10. Of this land then, concerning which I have spoken, it seemed to myself also, according as the priests said, that the greater part had been won as an addition by the Egyptians; for it was evident to me that the space between the aforesaid mountain-ranges, which lie above the city of Memphis, once was a gulf of the sea, like the regions about Ilion and Teuthrania and Ephesos and the plain of the Maiander, if it be permitted to compare small things with great; and small these are in comparison, for of the rivers which heaped up the soil in those regions none is worthy to be compared in volume with a single one of the mouths of the Nile, which has five mouths. 15 Moreover there are other rivers also, not in size at all equal to the Nile, which have performed great feats; of which I can mention the names of several, and especially the Acheloös, which flowing through Acarnania and so issuing out into the sea has already made half of the Echinades from islands into mainland. 11. Now there is in the land of Arabia, not far from Egypt, a gulf of the sea running in from that which is called the Erythraian Sea, very long and narrow, as I am about to tell. With respect to the length of the voyage along it, one who set out from the innermost point to sail out through it into the open sea, would spend forty days upon the voyage, using oars; 16 and with respect to breadth, where the gulf is broadest it is half a day's sail across: and there is in it an ebb and flow of tide every day. Just such another gulf I suppose that Egypt was, and that the one ran in towards Ethiopia from the Northern Sea, and the other, the Arabian, of which I am about to speak, 17 tended from the South towards Syria, the gulfs boring in so as almost to meet at their extreme points, and passing by one another with but a small space left between. If then the stream of the Nile should turn aside into this Arabian gulf, what would hinder that gulf from being filled up with silt as the river continued to flow, at all events within a period of twenty thousand years? indeed for my part I am of opinion that it would be filled up even within ten thousand years. How, then, in 18 all the time that has elapsed before I came into being should not a gulf be filled up even of much greater size than this by a river so great and so active?