The works had this peculiarity, that instead of rising above the earth, as did the ancient ramparts destined to defend a city from escalades, they, on the contrary, sank into it; and what created the height of the walls was the depth of the ditches.

It did not take long to make D'Artagnan perceive the superiority of such a system, which gives no advantage to cannon.
Besides, as the _fosses_ were lower than, or on a level with, the sea, these _fosses_ could be instantly inundated by means of subterranean sluices.

Otherwise, the works were almost complete, and a group of workmen, receiving orders from a man who appeared to be conductor of the works, were occupied in placing the last stones.

A bridge of planks thrown over the _fosses_ for the greater convenience of the maneuvers connected with the barrows, joined the interior to the exterior.

With an air of simple curiosity D'Artagnan asked if he might be permitted to cross the bridge, and he was told that no order prevented it.
Consequently he crossed the bridge, and advanced towards the group.
This group was superintended by the man whom D'Artagnan had already remarked, and who appeared to be the engineer-in-chief.