The coils are wound with copper wire (covered with silk), 10 mils.
It's so much more effective than rope, or wire, or chains.
For a wire exposed under the conditions observed by Elster and Geitel the emanation seems to be almost entirely derived from radium.
Some of the containers had a thin wire running around but most were standing alone.
It is essential that the paper covering be loose, so as to ensure that each wire is enclosed in a coating not of paper only, but also of air; the wires in fact are really insulated from each other by the dry air, the loose paper acting merely as a separator to prevent them from coming into contact.