Muffle Furnace: Electric, a Talc Tube Wound with Resistance Wire in a Plug-In Housing (Marsh, US 861,744, 1907)

A small electric muffle furnace from the man who invented nichrome. A talc tube wound with resistance wire, packed in silica inside a fire-clay shell, makes the heated chamber (the muffle). It slides into a metal housing on a post, and a plug-in head both feeds it current and locks it in place. The door drops flat to serve as a shelf. Result: a bench furnace that plugs into a lamp socket, with a muffle that can be pulled out and changed in moments. Source: A. L. Marsh (Hoskins Co.), US 861,744 (1907). Unknown: sizes, current and temperatures, and several materials. Asbestos fibre in the door and end disks: hazardous. Picture: the patent drawing.