Siemens Arc Lamp circa 1865
History of the Arc Lamp
Some say that Benjamin Franklin 'made' or rather demonstrated, the first arc light during his famous experiment with the key, the kite and the lightening, but I don’t think the claim is valid.
The electric arc lamp using carbon electrodes was first demonstrated by Sir Humphrey Davy in 1802 (or 1801 depending on whose history you read). He used two thousand battery cells wired in series as his electricity source. It was the first artificial electric light and produced an intense illumination which was subsequently used in the second half of the nineteenth century for lantern projectors, in microscopy and eventually street lighting.
For most of the nineteenth century the arc lamp couldn't be used ‘outside the laboratory’ at all. There were three reasons for this: the pure carbon rods burnt far too quickly, the lamps couldn't be regulated and finally there was no practical way of generating sufficient current to sustain the lamp over a long period.
The first requirement was to develop a type of carbon which burnt more slowly and a granulated carbon rod which proved satisfactory was developed by the French genius Léon Foucault (1819 – 1868) in 1844. (Prior to this scientists used an evacuated 'electric egg' with the carbon rods inserted in it to slow down the rate at which the carbon was consumed).
The second requirement for making a practical arc lamp was to find a solution to the problem of regulating the light which diminished as the carbon rods burnt and the gap between them increased until the electricity failed to jump the gap and the light first dimmed and then ceased. The solution was again supplied by Léon Foucault who invented the first self-regulating arc lamp in 1849 and made it more practical for laboratory use. The current was passed through an electro magnet in series with the carbon rods which became weaker as the carbon rods were consumed. When the power of the electro magnet decreased beyond a certain point the magnet keeper was released and operated a servo mechanism causing gear wheels to advance the carbons closer thereby increasing the current again which in turn re-energised the magnet and returned the keeper to its original position to repeat the process.
In 1851 Foucault and the optical instrument maker Jules Duboscq developed the first commercial arc lamp using this same principal of the electro magnet and keeper but substituted a clockwork gear mechanism for advancing the carbon rods in place of the servo mechanism. This Duboscq lamp was the world’s first manufactured electric light and is the example illustrated in all the textbooks covering this period.
The third problem of generating sufficient current to sustain a lamp over a long period took a further twenty-four years until the development of large Gramme dynamos.
There have been no examples of any arc lamps prior to the ‘Jablochkoff Candle’ (1876), offered for sale that I can trace by any major auction room, for which I have comprehensive catalogues stretching back over thirty years.
I have only managed to locate a tiny number of commercially produced arc lamps from this ‘laboratory period’ (up to 1876). I have found no early commercial examples illustrated on any museum website despite much time in surfing the web, lots from 1876 onwards of course; can you do better? (Some of the ‘best’ museum websites are not available to me without paying a subscription and I have not therefore been able to check these). I feel I can therefore state with confidence that any surviving commercial arc lamp made before 1876 is exceptionally rare and I don’t use the word ‘exceptionally’ lightly in this instance. One has to ask the question why?
After Faucault devised the first practical self-regulating arc lamp it was more than two decades before they could be economically viable. To produce arc lighting during this period required the use of hundreds of expensive batteries which were rapidly consumed by the production of the light.
By the 1870s cheaper batteries and practical generators were becoming available and engineers turned their attention once more to electric lighting. The first arc lamp to be used in large quantities was the 'Jablochkoff Candle' developed in 1876 by a Russian telegraph engineer. Consequently there was a gap of over twenty-seven years between the invention and any practical commercial use, until then the production of an arc light was confined to a few laboratories. This explains why surviving examples of the first lamps are so rare; few were made and even fewer survive.
The Siemens Arc Lamp
The Siemens official web site is very lightweight with regards to the history of its arc lamp production. It highlights the introduction of its differential arc lamps, quite properly in 1878, as they were a major advance on anything previously available, being able to operate in series, but it is silent on their earlier arc lamps. The lamp on offer here pre-dates their differential arc lamps probably by more than a decade with a very early serial number 129a. This lamp was designed for use in magic lanterns or spectroscopy in the laboratory or lecture hall and was manufactured to be operated by hundreds of batteries in series therefore pre-dating the development of powerful dynamos in the 1870s. The proof of this assertion is demonstrated by the terminals being marked Z and C for zinc and carbon, which makes this one of the very rare first electric lights – so rare that I cannot locate another example made by Siemens from this ‘battery period’ in any collection, public or private. (See the arc lamp made by Duboscq on this web site sold previously, with similar terminals marked Póle charbon and Póle zinc). The mechanism is very similar to that of the Duboscq arc lamp – the first commercial electric light introduced in 1851 - and is in perfect working order. The only significant defects are the broken terminal head on the zinc terminal and a vertical crack in the ebonite by the carbon terminal. Amazingly the lamp comes with its original key for the square nuts on the carbons and the terminals. Siemens Brothers London was started in 1863. Minimum height with the arcs closed 18.5” (47 cm) Maximum height with the arcs extended 25.5” (65 cm) square base 4.1” (10.5 cm)
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