What followed was a true boom of arc lighting. (Note: the inversed arc light above was a concept, it was never built) Around the same period the first practical incandescent light bulbs appeared, but they were not much competition either.Įarly incandescents only produced around 12 candlepower and were 20 times less energy efficient than arc lamps (it is interesting to note that 19th century arc lamps are still more energy efficient than todays incandescents, and that early 20th century arc lamps can even compete with today's compact fluorescents – but this is comparing apples with oranges since arc lights were not suited for use indoors). But arc lamps were brighter, cheaper and safer. That made the arc lamp much more reliable.Īt the end of the 1870s, gas light had conquered the streets of many cities, to a lesser degree still supported by earlier oil lamps. The rods were placed parallel to each other, which eliminated the need for complex mechanisms.
This was more or less resolved in the 1840s by self-regulating mechanisms (illustration at right), but it was the invention of the Yablochkov arc lamp in 1876 that resolved the issue completely. The carbon rods were consumed while the lamp was burning, which meant that the lamp had to be regulated by hand almost continuously to keep the distance between the rods constant. In the 1840s and 1850s, there were some public demonstrations with arc lights and a few early limited applications (notably in lighthouses, theatres and on large construction sites), but it was only with the arrival of useful electric generators (dynamos) at the end of the 1870s, that the arc lamp took off.Īround that time, the most important disadvantage of the arc lamp was also solved. The only sources of electricity during the first half of the 19th century were inefficient batteries, which made the use of arc lamps very impractical and excessively expensive. The problem was not so much the lamp itself, but the power source. In spite of the poor alternatives, it took more than 70 years before the arc lamp resulted in practical lighting devices on a large scale. Every street lamp had to be lit individually every night, and extinguished every morning. Streets were lit by oil or open flame gas lamps (or not at all).
Oil lamps had similar drawbacks, and the recent open flame gas lamps were only a modest improvement - the only advantages being that they were a little bit stronger and cleaner and only had to be ignited once. It took an awful lot of work to install, to light and to replace all those candles (see below), not to mention the toxic smoke, the smell, the heat, the built-up of soot and the risk of fire resulting from this. Large buildings, like theatres, were sometimes lit by hundreds or even thousands of candles. As a way of lighting up streets and large interior spaces, however, the technology sounded very promising. It was obvious that the powerful light of an arc lamp was absolutely unsuitable for use in a room. The discovery of the arc light was a spectacular feat, because the light it produced was incomparably stronger than anything else available at that time: candles, oil lamps and – appearing around the same time – open flame gas lights, which produced only 10 to 20 candlepower.
The temperature in the arc could rise to 4,000 degrees Celsius (more than 7,000 degrees Fahrenheit), the highest temperature that man achieved until the arrival of the atomic bomb. By further moving the rods just a little bit apart, the current flows through the vaporizing carbon and spans the air gap with an “arc” of intense light.Īn electric candle typically produced a light of 1,500 to 6,000 candlepower, which corresponds to the output of 11 to 43 modern 100-watt incandescent light bulbs. If two electrified carbon rods touch each other, some of the carbon vaporizes. In an incandescent light bulb (which was developed only 70 years later) an electric current is transferred over a filament, but in the case of an arc lamp this happens through the air instead. Davy, who can be considered the true founder of electric lighting, discovered that a blinding white light was produced by hooking up two charcoal rods to a battery, and bringing them very close together. The arc light (or “electric candle”) was invented and demonstrated by Sir Humphry Davy at the very beginning of the 19th century in England.
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