Six hours at a time in the sap
Officers relieved one another in the sap on roughly six-hour tours. Progress was slow but constant: the soil worked easily but averaged less than two feet down to water, so a strong parapet could not be kept closed up against the sap-roller. Three sappers were wounded. That night came the first attempt to destroy the New Ironsides by torpedo.
Major Brooks’ journal, OR I, 28, Pt. 1