A rare incandescent* Ebay Carbon Arc Light purchase is illustrated in the animation above. It is spring-loaded to maintain a gap between its carbons after "striking its arc," or momentarily touching its two electrified carbons toegether to initiate its blaze. A locking lever at its base maintains in place a wheel with two-degree separations in its teeth. The light may have been used in the mathematics department to demonstrate points on the circumference of a circle and probably as a light source by the Physics faculty? I do not know its age, but I suspect it is a nineteenth-century variety because of the large beads that are used to insulate its wiring tied to the carbon holders. Using beads is a very old method of insulating wires, which the following illustration of the artwork in the ancient Egyptian temple at Denderah** seems to demonstrate. Beads appear to be employed on the four connections running from an apparent battery on the far left to the four electric filament lamps behind the goddess Isis in the center.
Following the use of beads, cotton electric wire wrapping was used in the nineteenth century and also apparently in ancient Egypt as well, which the following illustration of an apparent cotton-wrapped cord running to three filament lamps seems to show. It was copied by one of Sir W. M. Flinders Petrie's artists from the wall of an ancient Denderah mastaba in 1898.*** The famous archaeologist's photograph is attached here to his discovery. For much more information on this illustration and the one above, see .The Electric Mirror on the Pharos Lighthouse and Other Ancient Lighting
Some examples of the nineteenth and early twentieth century methods of insulating electric wires are demonstrated in the animation below:
Below we see the old Karlova-University light powered by a modern electric heater. The architect of this website modified its wiring for that purpose. He uses this portable heater to limit the current drawn by the arc light, which acts as a short in series with the heater's resistive and inductively reactive coils. (Do not try to modify the wiring in one of these heaters for arc light use unless you are a qualified electronic technician or electrician.) This little foot-warmer supplies almost 9 amperes of AC current at nearly 110 volts, which equals nearly a kilowatt of power. The moving picture below demonstrates that the carbon arc lamp flashes brilliantly**** as a stream of electrons leap between the tips of its two carbons to start the fan as it completes the heater's circuit.
We interject the warning and illustration below for those who are not familiar with the damage to the eyes that some Ultra Violet rays from carbon arc lights like this one can generate. Never look directly at any carbon arc light without wearing protective eyewear. However, you do not need goggles for this webpage.
The guts of the portable heater (or carbon arc rheostat) is illustrated below. The squirrel cage fan prevents the heater's red-hot coils from burning up as it blows their heat away.
The labels in the photograph below identify the manufacturer and previous owner of the antique arc light. Dr. Paul Holitscher & Co. of Vienna produced it, perhaps when the Austro-Hungarian Empire still flourished? The Mathematics and Physics faculty at the University of Karlova apparently made use of it since the labels point in their direction. If anyone can supply any more information on this Ebay light, please pass it on to LarryBrianRadka@hotmail.com so he can post it on this webpage.
How or why this beautiful little carbon arc lamp departed Karlova University and found its way to Ebay, I do not know, but it is in good hands now!
*Many people believe that Edison’s type of light bulb is “the incandescent light,” but this is hardly the only type of incandescent light. An arc light is an incandescent light despite MacMillan’s Contemporary Dictionary, which defines an “incandescent lamp” as a “light bulb in which light is produced by passing an electric current through a thin high-resistance wire or filament, causing it to glow.” An incandescent light needs no bulb or filament. It can be generated by any material substance—including a gas or common air. The 1880 First Biennial Supplement to Johnson’s New Universal Cyclopaedia expounds on this subject further as follows:
“No material substance is a perfect conductor of electricity. All substances offer more or less resistance to the current flowing through them, and experience, accordingly, in transmitting the current, a greater or less elevation of temperature, dependent in degree on their conducting power, their dimensions, and the volume of the current. A comparatively good conductor of small cross-section and limited length may thus be heated to whiteness by a passing current, and so become a source of light. It thus appears that in endeavoring to apply the light of electricity to useful purposes resort may be had to contrivances of two distinct classes—viz, those which aim to utilize the electric arch [arc], which is an incandescent gas or vapor, and those which employ an incandescent solid.”
**See A. E. Mariette-Bey's Dendérah, Description Générale du Grand Temple du Cette Ville (Denderah, General Description of the Great Temple of this City), Paris 1875.
***See the publication: Dendereh 1898, Seventeenth Memoir of the Egyptian Exploration Fund, London 1900.
****Beware! Directly photographing arc lights may damage your modern digital camera! There is good reason to call an arc light a "Second Sun."