Father Nicholas Joseph Callan, Irish priest and scientist, is born on December 22, 1799, in Darver, County Louth. He is Professor of Natural Philosophy in Maynooth College in Maynooth, County Kildare from 1834, and is best known for his work on the induction coil.
Callan attends school at an academy in Dundalk. His local parish priest, Father Andrew Levins, then takes him in hand as an altar boy and Mass server, and sees him start the priesthood at Navan seminary. He enters Maynooth College in 1816. In his third year at Maynooth, he studies natural and experimental philosophy under Dr. Cornelius Denvir. He introduces the experimental method into his teaching, and has an interest in electricity and magnetism.
Callan is ordained a priest in 1823 and goes to Rome to study at Sapienza University, obtaining a doctorate in divinity in 1826. While in Rome he becomes acquainted with the work of the pioneers in electricity such as Luigi Galvani (1737–1798), who is a pioneer in bioelectricity, and Alessandro Volta (1745–1827), who is known especially for the development of the electric battery. In 1826, he returns to Maynooth as the new Professor of Natural Philosophy (now called physics), where he also begins working with electricity in his basement laboratory at the college.
Influenced by William Sturgeon and Michael Faraday, Callan begins work on the idea of the induction coil in 1834. He invents the first induction coil in 1836. An induction coil produces an intermittent high voltage alternating current from a low voltage direct current supply. It has a primary coil consisting of a few turns of thick wire wound around an iron core and subjected to a low voltage (usually from a battery). Wound on top of this is a secondary coil made up of many turns of thin wire. An iron armature and make-and-break mechanism repeatedly interrupts the current to the primary coil, producing a high voltage, rapidly alternating current in the secondary circuit.
Callan invents the induction coil because he needs to generate a higher level of electricity than currently available. He takes a bar of soft iron, about 2 feet long, and wraps it around with two lengths of copper wire, each about 200 feet long. He connects the beginning of the first coil to the beginning of the second. Finally, he connects a battery, much smaller than the enormous contrivance just described, to the beginning and end of winding one. He finds that when the battery contact is broken, a shock can be felt between the first terminal of the first coil and the second terminal of the second coil.
Further experimentation shows how the coil device can bring the shock from a small battery up the strength level of a big battery. So Callan tries making a bigger coil. With a battery of only 14 seven-inch plates, the device produces power enough for an electric shock “so strong that a person who took it felt the effects of it for several days.” He thinks of his creation as a kind of electromagnet, but what he actually makes is a primitive induction transformer.
Callan’s induction coil also uses an interrupter that consists of a rocking wire that repeatedly dips into a small cup of mercury (similar to the interrupters used by Charles Grafton Page). Because of the action of the interrupter, which can make and break the current going into the coil, he calls his device the “repeater.” Actually, this device is the world’s first transformer. He induces a high voltage in the second wire, starting with a low voltage in the adjacent first wire. The faster he interrupts the current, the bigger the spark. In 1837 he produces his giant induction machine using a mechanism from a clock to interrupt the current 20 times a second. It generates 15-inch sparks, an estimated 60,000 volts and the largest artificial bolt of electricity then seen.
Callan experiments with designing batteries after he finds the models available to him at the time to be insufficient for research in electromagnetism. Some previous batteries had used rare metals such as platinum or unresponsive materials like carbon and zinc. He finds that he can use inexpensive cast iron instead of platinum or carbon. For his Maynooth battery he uses iron casting for the outer casing and places a zinc plate in a porous pot (a pot that had an inside and outside chamber for holding two different types of acid) in the centre. Using a single fluid cell he disposes of the porous pot and two different fluids. He is able to build a battery with just a single solution.
While experimenting with batteries, Callan also builds the world’s largest battery at that time. To construct this battery, he joins together 577 individual batteries (“cells“), which use over 30 gallons of acid. Since instruments for measuring current or voltages have not yet been invented, he measures the strength of a battery by measuring how much weight his electromagnet can lift when powered by the battery. Using his giant battery, his electromagnet lifts 2 tons. The Maynooth battery goes into commercial production in London. He also discovers an early form of galvanisation to protect iron from rusting when he is experimenting on battery design, and he patents the idea.
Callan dies at the age of 64 in Maynooth, County Kildare, on January 10, 1864. He is buried in the cemetery in St. Patrick’s College, Maynooth.
The Callan Building on the north campus of NUI Maynooth, a university which is part of St. Patrick’s College until 1997, is named in his honour. In addition, Callan Hall in the south campus, is used through the 1990s for first year science lectures including experimental & mathematical physics, chemistry and biology. The Nicholas Callan Memorial Prize is an annual prize awarded to the best final year student in Experimental Physics.