Titus Livius (Livy), The History of Rome, Book 28
Cyrus Evans, Ed.

30. During the time of these transactions, Hanno, the lieutenant-general of Mago, having been sent from Gades to the river Baetis with a small body of Africans, by tempting the Spaniards with money, armed as many as four thousand men; [2] but afterwards, being deprived of his camp by Lucius Marcius, and losing the principal part of his troops in the confusion occasioned by its capture, and some also in the flight, for the cavalry pursued them closely while they were dispersed, he made his escape with a few attendants. [3] During these transactions on the river Baetis, Laelius in the mean time, sailing out of the straits into the ocean, came with his fleet before Carteia, a city situated on the coast of the ocean, where the sea begins to expand itself, after being confined in a narrow strait. [4] He had entertained hopes of having Gades betrayed to him without a contest, persons having come unsolicited into the Roman camp to make promises to that effect, as has been before mentioned. The plot was discovered before it was ripe, and all having been apprehended, were placed by Mago in the hands of Adherbal the praetor, to be conveyed to Carthage. [5] Adherbal, having put the conspirators on board a quinquereme, sent it in advance, because it sailed slower than a trireme, and followed himself at a moderate distance with eight triremes. [6] The quinquereme was just entering the strait, when Laelius, who had himself also sailed out of the harbour of Carteia in a quinquereme, followed by seven triremes, bore down upon Adherbal and his triremes, feeling assured that the trireme, when once caught in the rapid strait, would not be able to return against the opposing current. The Carthaginian, alarmed by the suddenness of the affair, hesitated for some little time whether he should follow the trireme, or turn his prows against the enemy. [7] This very delay put it out of his power to decline an action, for they were now within a weapon's cast, and the enemy were bearing down upon him on all sides. [8] The current also had rendered it impossible to manage the ships. Nor was the action like a naval engagement, inasmuch as it was in no respect subject to the control of the will, nor afforded any opportunity for the exercise of skill or method. [9] The nature of the strait and the tide, which solely and en- [p. 1204]tirely governed the contest, carried the ships against those of their own and the enemy's party indiscriminately, though striving in a contrary direction; so that you might see one ship which was flying whirled back by an eddy and driven against the victors, and another which was engaged in pursuit, if it had fallen into an opposite current, turning itself away as if for flight. [10] And when actually engaged, one ship while bearing down upon another with its beak directed against it, assuming an oblique position itself, received a stroke from the beak of the other; while another which lay with its side exposed to the enemy, receiving a sudden impulse, was turned round so as to present its prow. [11] While the triremes were thus engaged in a doubtful and uncertain contest, in which every thing was governed by chance, the Roman quinquereme, whether being more manageable in consequence of its weight, or by means of more banks of oars making its way through the eddies, sunk two triremes, and swept off the oars from one side of another, while sailing by it with great violence. [12] The rest too, had they come in its way, it would have disabled; but Adherbal, with his remaining four ships, sailed over into Africa.