Thomas Wilhelm, A Military Dictionary and Gazetteer
“ An underground passage, whether cut in the soil or built in masonry; it forms the communication between the inner and exterior works of a fortified place. When prepared for defense, it is a defensive gallery. In military mines, galleries are the underground passages leading to and connecting the mine chambers. Scarp and counterscarp galleries are covered passages built in the scarp and counterscarp to give a flanking fire in the ditch. ”
