There are two sets of carbons in this design, each with its own pair of feedwires. Only one set is in operation at a time. When the first set is burned out the second will come into operation.
To facilitate this, the lamp is on a swiveling horizontal arm with a counterweight. (The iron ball on the pole-end of the arm)
Likely a form of advertising. But for what?
Colorized photos submitted by members.
Submitted byDaveon Thu, 04/12/2018 – 2:35pm.
Circa 1905. St. John Street, Quebec. Rue Saint-Jean at Côte du Palais in Quebec City, home to the drugstores of P. Mathie and J.E. Livernois. 8×10 inch dry plate glass negative, Detroit Photographic Company.View full size.
It appears that the lamp maintainer would climb the rungs on the pole to the level of the lamp, then swing the arm 180 degrees to bring the lamp within easy reach. It looks like the lamp swings counterclockwise when viewed from above, i.e. away from the photographer.
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Remaining mystery is the four wires to the lamp assembly. This hints at some sort of automatically-adjusting arc mechanism. (Two wires are for the arc carbons, two for the can-like mechanism above the lamp itself.)
The streetlight is an arc lamp, which requires frequent replacement of the carbon electrodes and other adjustments.
These early arcs burned up their carbons in about 8 hours, so with the paired sets of rods 16 hours could be had, then the rods changed daily. Later designs with improved air flow didnt consume their carbon as quickly and could be run for about 150 hours.
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