Note 97 — Chapter VIII

The usual rate of advance of a sap is from 2 to 4 feet per hour, depending on the nature of the soil and the amount of excavation necessary. The latter must, of course, depend on due cover for the party being provided. The Official History states that breastworks, or, more correctly speaking, “parapets” had to be built up, 5 feet high and 4 feet thick, with sand-bags, as ordinary digging was impossible in the rocky formation of 203 Metre Hill. This accounts for the slow rate of progress. Though it is not clear from the narrative, the type of sap was probably that known as “double.”