A circular wick type was invented by Argand. It apparently eliminated most of the smoke from whale oil lamps. In Norway, I saw old kerosine lamps with flat and round wicks. The ones with round wicks had much smaller bulges around the flame in their chimneys, which looks as though they worked much better. The wick itself was actually flat, but it was fed upward throw a circular hole that bent it in a circle.
Lamps are incandescent like simple electric lights, so the key to efficiency is temperature. The chimney makes it brighter by drawing air. But if there is too much air, there are no carbon particles, like a gas stove. It is the carbon lamp black in the flame that radiates the light. Then there needs to be enough air and heat farther up in the flame to burn away the lamp black, or everything nearby will turn black and absorb the light, like the old part of the Norwegian farm house or a lamp chimney when the lamp has been turned too high. The flow needs to be laminar. If the wick is too high or there is too much flow for any other reason, the flow becomes turbulent, and then there are spots in it where carbon escapes. That happens to non-smokeless candles if the wicks are not trimmed in time. In smokeless candles the wick bends over and burns to the proper length at the edge of the flame where there is both air and heat.
Three-Day Week
The Three-Day Week was one of several measures introduced in the United Kingdom in 1973–1974 by Edward Heath's Conservative government to conserve electricity, the generation of which was severely restricted owing to industrial action by coal miners and railway workers. From 1 January 1974, commercial users of electricity were limited to three specified consecutive days' consumption each week and prohibited from working longer hours on those days. Services deemed essential (e.g. hospitals, dat...