Charles P Lamb wrote:

My first guess is using resistance
but I would guess the electricity would be more likely to take the path
around the link than across the touching faces.

It is and why it works was explained by others. Saw a film where they made
chains and it was *really* impressive. Not that kind of neglace chains, but
*real* chains. For ships anchors. It's a hard work to connect the links (it
was some kind of carussell (SP?). The links were about 500mm long, diameter
something like 100mm or more. Big presses and the welding machine ... I
don't want to pay their electricity-bill! :-)

Nick
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