Mid″feath′er (?), n. 1. (Steam Boilers) A vertical water space in a fire box or combustion chamber.
2. (Mining) A support for the center of a tunnel.
Webster's Dictionary 1913
Mid″feath′er (?), n. 1. (Steam Boilers) A vertical water space in a fire box or combustion chamber.
2. (Mining) A support for the center of a tunnel.