As it was rather dark, on account of the shade of the trees, the driver did not observe this jolt, and he was just beginning to put his horses to the trot, as they were leaving the bridge, when the forward wheels struck down heavily into the hollow, giving the front of the coach a sudden pitch forward and downward.

Marco grasped the iron bar at his end of the seat, and saved himself; and the driver, who was habitually on his guard, had his feet so braced against the fender before him, that he would not have fallen.

But the poor sailor, entirely unprepared for the shock, and perhaps unable to resist it if he had been prepared, pitched forward, lost his hold, went over the fender, and was tumbling down, as the driver had predicted, head foremost, under the horses' heels.
The driver seized hold of him with one hand, but finding this insufficient dropped his reins and tried to grasp him with both.

In doing it, however, he lost his own balance and went over too.

He, of course, let go of the sailor, when he found that he was going himself.
The sailor fell heavily and helplessly between the pole and the side of one of the horses, to the ground.