The subject of these lines may be found in Caes. B.C. I. 54, from which they are in part derived, though probably at second hand. The reference is to Caesar's tactics after the floods in the plain around Ilerda. He built a number of coracles after the British fashion, and had them conveyed to a point on the right bank of the Sicoris, twenty-two miles from his camp. In these boats he sent a number of men across the river, who fortified some rising ground. Then he sent a legion across and started the building of a bridge from both sides at once: hue legionem postea traiecit atque ex utraque parte pontem institutum biduo perfecit.