Hoplopœia,[18] he places the ocean in a circle round the border of Achilles’ shield. Another proof of the extent of his knowledge, is his acquaintance with the ebb and flow of the sea, calling it “the ebbing ocean.”[19] Again, “Each day she thrice disgorges, and again Thrice drinks, insatiate, the deluge down.”[20] The assertion of thrice, instead of twice, is either an error of the author, or a blunder of the scribe, but the phenomenon is the same, and the expression soft-flowing,[21] has reference to the flood-tide, which has a gentle swell, and does not flow with a full rush. Posidonius believes that where Homer describes the rocks as at one time covered with the waves, and at another left bare, and when he compares the ocean to a river, he alludes to the flow of the ocean. The first supposition is correct, but for the second there is no ground; inasmuch as there can be no comparison between the flow, much less the ebb of the sea, and the current of a river. There is more probability in the explanation of Crates, that Homer describes the whole ocean as deep-flowing, ebbing, and also calls it a river, and that he also describes a part of the ocean as a river, and the flow of a river; and that he is speaking of a part, and not the whole, when he thus writes:— “When down the smooth Oceanus impell’d By prosperous gales, my galley, once again, Cleaving the billows of the spacious deep, Had reach’d the Ææan isle.”[22] He does not, however, mean the whole, but the flow of the river in the ocean, which forms but a part of the ocean. Crates says, he speaks of an estuary or gulf, extending from the winter tropic towards the south pole.[23] Now any one quitting this, might still be in the ocean; but for a person to leave the whole and still to be in the whole, is an impossibility. But Homer says, that leaving the flow of the river, the ship entered on the waves of the sea, which is the same as the ocean. If you take it otherwise you make him say, that departing from the ocean he came to the ocean. But this requires further discussion.