Page:Incandescent electric lighting- A practical description of the Edison system.djvu/42

 block of plaster held in place by spurs or projections on the bottom of the tube which supports the carbon filament.

About the outside of this plaster base, is arranged a thin shell of metal pressed into the form of a screw, and to which is attached the end of a small copper wire, the other end of this wire being melted or soldered to the free end of one of the bits of platinum supporting the carbon filament; the other bit of platinum being in a like manner connected by a piece of copper wire to a metal button on the bottom of the plaster base of the lamp.

Thus to follow the circuit of the completed lamp, we could start at the metal screw shell on the outside of the plaster base, thence through the copper wire attached to it to the small platinum wire embedded in the top of the glass tube, through the carbon filament secured to it, to the opposite platinum wire and down the copper wire secured thereto, terminating at the metal button on the bottom of the plaster base, which is insulated