Marco was an expert climber.

He had learned this art in his gymnasium at New York; so that he had no fears in respect to his being able to get down and back again.

The only danger was, lest he might frighten the horses again and set them to running anew.
After a moment's reflection, he concluded that at any rate he would try it; so he cautiously stepped over the fender and clambered down.
When his feet reached the pole, he rested them a moment upon it, and clung with his hands to the fender and other parts of the front of the coach.

He found his position here more unstable than he had expected; for the coach being upon springs, the forward part rose and fell with many jerks and surges, as the horses traveled swiftly along, while the pole was held in its position straight and firm.

Thus the different parts of his body were connected with different systems of motion, which made his position very uncomfortable.
He found, however, after a moment's pause, that he could stand, and probably walk upon the pole; so he advanced cautiously, putting his hands on the backs of the horses, and walking along on the pole between them.