He experimented with bundles of iron wires variously insulated, also with sheet-iron rolled cylindrically and covered with iron wire wound concentrically. 弗兰克·刘易斯·戴尔.爱迪生的生平和发明.
The cold compressed air then passes through pipes 4 and 5, pipe 5 being arranged concentrically within a larger coil 7. Edward W. Byrn.十九世纪发明进展.