Passage of Ditches

In siege operations the pa age of a dry ditch consists in the descent (which is by a blindage, if the ditch is not too deep, or a blindage and gallery for deep ditches) and a full sap, which leads from the outlet of the descent to the bottom of the breach. The pa age of a wet ditch is more difficult, and specially perilous if the besieged can produce sudden freshets by flood-gates or other contrivance. The method usually followed is to build a dike or bridge of fascines and hurdles acro the ditch. The abutment for this bridge is formed by excavating a grand gallery behind the counterscarp and throwing the earth taken from it into the ditch through the outlet of the descent . The dike is carried forward from this abutment by sappers, who work on a raft carrying a musket-proof mask on the side of the enemy. A gabionade parapet on the exposed side of the dike serves to protect the men in bringing forward the fascines, hurdles, etc., to extend the dike.