| Webster's Online Dictionary |
| Expressions | Domain | Definition | |
| Hirschback method | Mining | A method for draining combustible gases from coal seams in which superjacent entries are developed over the coal seam being mined. The entries are located from about 80 to 138 ft (24 to 42 m) above the seams to be mined and are often supplemented with up or down boreholes drilled perpendicular to the walls of the entries. Also known as the superjacent roadway system. (references) | |
Source: compiled by the editor from various references; see credits. | Top | ||
