As used in this subpart, all terms not defined herein shall have the meaning given them in the Act and in subpart A of this part.

(a) Brass or bronze means any metal alloy containing copper as its predominant constituent, and lesser amounts of zinc, tin, lead, or other metals.

(b) Reverberatory furnace includes the following types of reverberatory furnaces: Stationary, rotating, rocking, and tilting.

(c) Electric furnace means any furnace which uses electricity to produce over 50 percent of the heat required in the production of refined brass or bronze.

(d) Blast furnace means any furnace used to recover metal from slag.