Suddenly, from the midst of the clumps of reeds that rise at irregular intervals along the length of the tongue of land, the cry of night-birds goes up--cries identical with those that had resounded from the summits of Glen-Clan. Upon the signal, the muffled sounds of rapid hatchet strokes are heard. They teem to be the answer given to the cries of the night-birds. Instantly the seemingly solid walk sinks at scores of places under the feet of the marching soldiers. Woe is those who happen to find themselves over these hidden traps, that are constructed of wooden beams and strong chains concealed under a layer of sward! The scheme, devised by Vortigern, proves successful. The movable bridges can, at will, either support the weight of the troops that march over them, or tip over under their tread, by the dexterous knocking from under the loose boards the wooden pegs that are their only support. Plunged in the water up to their necks, Vortigern and a large number of stout-hearted men of his tribe have held themselves motionless, mute and invisible in the center of the clumps of reeds that border the jetty near each of the traps. When the jetty is entirely covered with Frankish soldiers, the hatchets are, at a signal, plied with energy; the pegs drop out; and the passage is suddenly cut up by scores of gaps twenty feet wide. Pell-mell foot soldiers, cavalrymen and their horses tumble to the bottom of these suddenly opened ditches, and are received thereupon by the sharp points of piles providently sunk at the bottom.