Summary: THE emergence of the high-frequency induction furnace from the scientific worker's laboratory into the world of industrial production has aroused widespread interest. True, induction furnaces have long found successful application in the commercial world, but these have all been characterised by some form of iron core and have operated at relatively low frequencies. Although the possibilities of high-frequency inductive heating were demonstrated so far back as 1905 by Schneider, not much advance was made until 1919, when. Northrup published an authoritative paper which renewed interest in the subject. How rapid has been the progress from that date may be judged from the fact that in 1925 high-frequency furnaces capable of handling 6oo-lb. charges of nickel alloys were in operation.