You Don't know Francesco!

Even if you're a radio geek, odds are low that you know the name Francesco Zantedeschi. Even if you're an Italian radio engineer, Zantedeschi's contributions are so arcane he is still probably unknown to you. If I had to sum up the 'thesis' of my blog is that no one person invents anything. All progress by definition is cumulative. So I like to dig up obscure, seemingly trivial contributions and put them in context.

Zantedeschi was born in 1798 in Dolcè, near Verona, Italy. Zantedeschi was a  professor of physics in Venice.  He had interests outside of magnatism,his accomplishments in Botany were also substantial. The African flower (Zantedeschia Sprengel Araceae) is named for him .Many of his published works are online... in Italian. Bummer.

After his own schooling was complete he became a clerk, then a high school teacher. But his interest in physics brought him further into academia. He became a pro tempore professor at the University of Padua in 1849 teaching physics. While there, Francesco Zantedeschi studied light, eat, electricity and magnetism. While there, he became the first to suggest a connection between light, electricity and magnetism. I know that Michael Faraday gets all the big credit but he wasn't alone. So let's rewind to 1829. Zantedeschi published papers on the production of electric currents in a closed circuit caused by the approach and withdrawal of a magnet. This was just 2 years before Michael Faraday's induction experiments. Zantedeschi  was aware of Faraday's work and even bought himself a Ruhmkorff Coil to replicate Faraday's experiments.He wasn't a glory hog, he wanted to replicate the test because it's good science.

Zantedeschi  held the position at Padua until 1853 when he finally resigned due to his diminishing eyesight. But he kept working privately. He published a 16 page paper in 1859, defending Gian Domenico Romagnosi. At the time Hans Christian Ørsted was falsely claiming to have discovered the magnetic effect of the electric current. Ørsteddid discover it in 1820 but Romagnosi discovered it in 1802. This wasn't just nationalism for Zantedeschi . This was his legacy. Anyone attacking the work of his predecessors was also inherently undermining his own claims. Zantedeschi died at Padua in 1873 at the age of 75.

The Induction Coil (Part 4)

Welcome to Part Four, the conclusion of this 4 part series on induction coils.

The book History of Induction by Charles Page assessed the later improvements to the induction coil as a series of advances in each of it's component parts. Btu crucially, it's power and thus versatility came from advances in the circuit breaker. So page itemizes a set of  twelve, which he overwhelmingly he attributed to himself. By his own count he invented 15 different kinds of circuit breakers before 1840. I'll list them fully because it's actually pretty important.

First: The first mechanical circuit-breaker used with an induction coil  (M. Masson)

Second: The first automatic or self-acting circuit-breaker used with an induction coil (C. Page)

Third: The first circuit-breaker used with an induction coil having a primary and secondary circuit. (C. Page)

Fourth: The first independent automatic circuit-breaker used with an induction coil (C. Page)

Fifth: The first attached automatic circuit-breaker used with an induction coil (J. McGauley)

Sixth: The first adjustable automatic circuit-breaker used with an induction coil (C. Page)

Seventh: The first mercurial circuit-breaker used with an induction coil (C. Page)

Eighth: The first automatic attached circuit-breaker, in which the retractile force of the hammer was adjustable(C. Page).

Ninth: The first spark-arresting circuit-breaker used with an induction coil (C. Page)

Tenth: The first attached circuit-breaker which combined the means of adjusting the retractile force of the hammer and its distance from the magnet. (C. Page)

Eleventh: The first automatic circuit-breaker with an induction coil for remedial purposes (C. Page)

Page certainly thought highly of his own contributions. But he was very keen on crediting McGauley and Masson (but not Callan or anyone else). There is a reason for this.  Page wrote the History of Induction in 1867. In 1864 Ruhmkorff was awarded the Volta Prize a 50,000-franc prize by Napoleon III for the most important discovery in the application of electricity - the Induction Coil. Page was furious and righteously; his book was an act of vengeance. When he wrote the history he was trying to certify his own significance but also to shame Ruhmkorff, and those that awarded him. Ruhmkorff's act of invention was a myth. The induction coil had already been available at retail for a decade when he "invented" it. In 1872 Jean Baptiste Alexandre Baille wrote his own history of the Induction coil and concluded:

"With the exception of Fizeau's condenser, the electrostatic coil is an American invention, and the so-called Ruhnikorff coil was commenced and perfected in the United States, Professor Page developing the electrostatic properties, and Edward S. Ritchie, of Boston, consummating the perfection of the instrument, to an extent far exceeding anything known in Europe."

Ruhmkorff patented his first induction coil in 1851. It used long copper windings and could produce a 2 inch spark. In 1859 a Mr. Gassoit published in France, an account of the Edward Samuel Ritchie coils. Then Ruhmkorff had the opportunity to examine a superior induction coil developed by the American inventor  Ritchie in 1860. A Professor McCulloh of Columbia College brought a Ritchie Coil to Paris. Ruhmkorff examined it and  that led him (understandably) to incorporate some of Ritchie's improvements and to change his induction coil.  His improvements included glass insulation, larger coils, a current reverser  (Rheotrope) to change the direction of the primary circuit, and he also added a capacitor.

The improvements were all from page, and Ritchie except for two: The Rheotrope was an invention of M. Masson from 1834.  The capacitor (condenser) has two different etymologies.  It was French physicist, Armand Hippolyte Louis Fizeau recommended using the capacitor. But that development also was not wholly original.  In 1853 Jonathan Nash Hearder exhibited an induction coil with a capacitor. Though little information is available, presumably that capacitor resonated the secondary coil producing yet more voltage. Fizeau developed that improvement separately and patented it in 1853. The awarded coil could produce sparks over 12 inches long.

Why does all this matter to radio? The history of the induction coil is the history of the spark gap transmitter. The devices are synonymous. In 1895 Marconi's first transmitter consisted of an induction coil connected between a wire antenna and ground, with a spark gap across it. The most basic spark-gap transmitter is a spark gap connected across an oscillatory circuit consisting of a capacitor and an inductor in series or parallel. I'll cite an obscure article by Frank Butler, the Chief Assistant to Dr. Lee De Forest wrote an article in 1924 titled Making Wireless History for Radio Broadcast Magazine.

"The apparatus for sending was a Ruhmkorff induction coil with a vibrator on one end. Direct current was used in the coil and the vibrator converted it into alternating current of slow oscillations as compared with those used to-day. The power used then to send six miles would to-day send almost six thousand."

The Induction Coil (Part 3)

It's hard to understand why Ruhmkorff is most often credited with the invention of the induction coil in 1851. Joseph Henry invented it in 1831. Then both Charles Page, and Nicholas Callan invented it in 1836. It's especially strange since Ruhmkorff based the design he patented on a different earlier induction coil made by Edward Samuel Ritchie. It relates back to that cranking mechanism. Let me back up to Callan. You may recall in Part 2 he built what he called a "repeater." That was a mechanism that could make and break the electrical circuit in a cycle. What was important about that was that it increased the power of the output spark. Since electric motors did not yet exist everything that moved moved by wind, water, steam, gravity or muscle. So all these devices needed to be cranked.

The earliest cranked inductor was probably built by a French engineer named  Antoine-Hippolyte Pixii. He built a simple dynamo based a description of Faraday's 1831 device. Faraday had mounted a copper disk on an axle and spun it between the poles of a magnet. This generated an electric current. In 1832 Pixii modified that so that the magnet was rotated by a hand crank and he positioned it such that its north and south poles passed over two pieces of iron wrapped with coiled wire. It's those coils of wire that are so important. Pixii even determined that each pole produced a separate pulse of current i.e. This was an AC device! Pixii had previously been hired by both Andre
Ampere and Claude Pouilett to build their own instruments.  So this was not his first foray.

Joseph Saxton of Philadelphia built a unit based on the Pixii design. His first devices dates to 1832, but he had but the basic design to paper at least a year earlier. He reversed the mechanism instead spinning the horseshoe magnet and leaving the coils stationary. His went through several revisions, but the basic device was described in detail in his 1874 memoir read before the National Sciences Academy by none other than Joseph Henry.

"Mr. Saxton fastened the U to a revolving axis passing through its crown, to which a rapid rotation could be given by means of a driving wheel and pulley. In order, however, to obtain manifestations of the induced currents produced in the copper-wire, the two ends of the coils were so soldered together, as to give a single current in one direction through the entire length of the coils. One of the remaining ends was then permanently soldered to a circular disk fastened concentrically to the revolving axis by an insulating collar, with its plane perpendicular to it. This plate dipped into a cup of mercury. The other end of the wire was soldered directly to the revolving shaft or axis."

This cranking and rotating of the magnet gets closer and closer to a dynamo. A is just an electrical generator that uses rotating coils of wire and magnets to convert mechanical rotation into electric current. It's output is governed by Faraday's law. That law is as follows: The EMF generated is proportional to the rate of change of the magnetic flux. That's exactly what Callan observed. The faster he could make and break the circuit, the greater the current output by his cranking. All this leaves me with one big question. How do we get from the 1836 "invention" of the induction coil to the 1856 "invention" of the induction coil?

In 1835 Edward Samuel Ritchie and Edmond Clarke were fighting it out over who made the better induction coil yet both were based on the work of Pixii. In 1838 Daniel Davis made a slightly modified machine based on the published accounts of Page and Sturgeon. Davis actually published a 72-page catalog filled with  models of home electrical induction devices. These were presumably for the purpose of shocking oneself or ones friends and family for "medical" purposes or just the schadenfreude. In 1839 a German doctor named Christian Neef et De La Rive innovated a new make/break mechanism to increase output.  It was a hammer break mechanism. It consisted of a spring contact that operated automatically to break the electrical circuit when displaced by the action of the electromagnet. William Sturgeon published the first English version of the Neef "repeater" in 1839. Interestingly Page credits the so-called Neef-Hammer to Prof James William McGauley. It then further states that Ruhmkorff stole McGauley's circuit breaker.

After all of that progress, there is still a 18-year gap still remaining between that last material improvement and Ruhmkorff "invention" of the induction coil. In truth Major improvements essentially stop before 1940. Even circuit breakers have little improvement until Foucault  in 1856. Golding Bird made some minor refinements to McGauley's device in 1838. Ernst Neeff also gets a mention for an equally minor adjustment in 1839. In 1842 W.T. Henley proffered a coil that worked ran on a clock-work mechanism. But that mechanism was actually from Rev. F. Lockey. It was more of an amalgam than an invention. In 1842 Page was discharging electrical flashes in vacuum tubes and working on electric motors.

The reason that improvements stopped is that the device had been "perfected." It was fully functional. It was moving out of the lab and into commercial use.  That's where it remained for almost 2 decades. By 1843 both Thomas Wright and Neef were boiling water with an induction coil. In the year 1850 Werner Siemens patented a dial telegraph and an alarm for it which used an automatic vibratory circuit breaker which also drew from McGauley's circuit breaker. All manner of devices were built, stocked shipped and sold: telegraphs, alarms, bells, buzzers, X-ray devices, electroshock.. all manner of consumer and medical devices used induction coils. All these products and services apparently awaited their retroactive post-Ruhmkorff invention.

The Induction Coil (Part 1)

Heinrich Daniel Rühmkorff removed the umlaut from his last name when he moved to England. Despite the timing, it was probably convenience and not politics as neither language uses them. It was a pragmatic decision, a common quality in engineers. He is often credited with the invention of the induction coil. it's not that simple of course, but the writers of history are pragmatic in an entirely different way.We'll get back to Mr. Rühmkorff in Part 2.

The image above is from The Handbook of Electricity in Medicine by W. H. Guilleminot, printed in 1906.  The Ruhmkorff coil is now known as an induction coil, and it was the invention that directly led to the modern electric transformer. Coiled wire behaves very differently under different circumstances. It is different from the Tesla coil (1891), or the Henry coil (1831). The mad scientists of the day liked to generate sparks. They also used the Holtz machine and the Voss machine. These were not props, but all early stages in the development of electronics.None the less these nuts seemed to enjoy shocking each other and themselves.  Let me quote Joseph Henry

"If the extreme poles of this compound arrangement be terminated by the copper handles, and these be brought in contact, holding one in each hand, a deflagration of the metal will be produced, and a thrilling sensation, scarcely supportable, felt in each arm."

The first real induction coil was invented by Charles Grafton Page and patented in 1836. Page had been trying to improve Joseph Henry’s calorimeter [Which was based on Hare's calorimeter.] There are some sources that suggest he was also familiar with Faraday's concept of self-induction but this is apocryphal. Henry developed a number of copper coil experiments. Page was a student at Harvard at the time and was studying the medical application of electro-therapy and took an interest in Henry's idea of fun. 

Page wound a coil of copper ribbon through a series of cups filled with mercury using them as electrical connectors. One terminal of the battery was then connected to the innermost cup of mercury and the other terminal to different cups elsewhere along the length of the coil. I'll quote Wikipedia on how Page liked to shock himself with the resulting product.

"He held a metal wand in each hand, and put these wands into the same two cups as where the battery terminals went — or any other pair of cups. When an assistant removed one of the battery terminals, stopping the current from going in the spiral, Page received a shock. He reported stronger shocks when his hands covered more of the spirals length than where direct battery current went. He even felt shocks from parts of the spiral where no direct battery current passed."

Working concurrently on a similar set of coils was British experimenter William Sturgeon. Sturgeon was familiar with Page and even reprinted Page's article in his journal Annals of Electricity. Sturgeon devised coils that were adaptations of Page's instrument, where battery current flowed through one, inner, segment of a coil, and electrical shock was taken from the entire length of a coil. Page in turn developed a coil  experiment with two wires, a primary and a secondary. The first was a primary coil heavy gauge copper wire wrapped around a bundle of thin iron rods. The second was a coil of fine wire wrapped around the outside of the primary coil with silk insulation in between them. Page  published an account of this which he documented in a paper titled The Compound Electro-Magnet and Electrotome. In the 1840s he worked at the US patent office and he build telegraph equipment for Samuel Morse

Sadly external events drove him out of science.  In 1863 Union soldiers in the trashed his lab and he quit the business. Virginia had joined the Confederacy in 1861 moving the war front to northern Virginia. It's likely his property was trashed in the retreat in the spring of 1863. he never returned to science. He died 5 years later at the age of 56.