A Vintage Ebay Bausch & Lomb Electric "Mechanical Feed Arc Lamp"
Above is a close-up picture of the clock mechanism inside the box with the windup key on the side of the arc light illustrated above. It drives the chains that keep the carbons continuously separated at the proper distance to maintain the arc. Note the beads used for insulating the wire. This was probably the first type of insulation ever used for electrical wiring, at the dawn of modern electrical practice in the eighteenth century as well as in antiquity.
For much more on carbon arc lights, and especially those in antiquity, read The Electric Mirror.