Charles Grafton Page and His Shocking Coil
Thomas B. Greenslade, Jr.
Kenyon College, Gambier, Ohio 43022 USA
Recently I came across the piece of apparatus in Figure 1 on a shelf in my museum. It had come to me from Colgate University in 2005, and was clearly an early form of induction coil. This is an account of how I learned more about this device and its relatives. It is composed of two parts.
It is composed of two parts. The larger portion is what today we would call a step-up transformer, with a primary coil of relatively few turns, and a secondary coil around it with many turns of fine wire. Running through the primary is a bundle of iron wires that take the place of the core of a modern transformer; the wires are used instead of a solid soft iron core to prevent the formation of eddy currents.
When the apparatus was built, alternating currents were unknown, and it has a mechanism for turning direct current into the alternating voltage used to drive the primary. At the end of the device is a small U-shaped electromagnet that is connected in series with the primary coil. This attracts a T-shaped piece of iron that is attached to a flexible metal reed. As the iron strip is pulled down, it breaks a contact, cutting off the current to the magnet and the primary. As soon as this happens, the reed springs back, reestablishing the current. The wave shape is roughly that of a square wave, which, of course, has a sine wave of the same frequency as its primary Fourier component. The frequency of the resulting alternating current is controlled by the elastic properties of the reed and the mass attached to it.
This differs from the “modern” induction coil only by the capacitor that is connected across the make-and-break contacts. In the 1869 Apps induction coil in my collection (Figure 2), also from Colgate, the flat capacitor, made of sheets of tinfoil and varnished paper, is contained in the base. This refinement, due to the Parisian apparatus manufacturer, Heinrich Daniel Ruhmkorff (1803-1877), serves to reduce sparking at the contacts, and also makes the output asymmetrical,
so that a positive and a negative polarity are available across the output of the secondary. Notice how the magnetic field produced by the primary coil is used to drive the make and break mechanism that is used to produce the alternating voltage.
Eventually I located the apparatus in the 1860 catalogue of Edward S. Ritchie of Boston. In the 1869 catalogue it is listed as a “Double Helices, or shocker; … with vibrating electrotome. The core is a bundle of iron wires, which can be drawn out, regulating the intensity of the shock; 8.50 and 7.50”. By 1881 the catalogue was calling the apparatus “Page’s Shocker” (Ref. 1) The only difference was that the vibrating Electrotome (Ref. 2) in the woodcut in the catalogue is placed at right angles to the one in my collection.
At this point I decided to look at the mother lode of information about early magneto-electric devices, the various editions of Daniel Davis’s Manual of Magnetism. In 1846 he wrote a supplement on the “Medical Applications of Electricity”. Figure 3 shows the “Electromagnetic Apparatus and Vibrating Armature”, along with the Daniell cell used to excite it, and the connection to the hand and to an iron slipper. Devotees of Davis apparatus will immediately recognize the characteristic brass finial and the brass ball feet.
Davis points out that the frequency of the operation can also be controlled by the setting of the screw, marked “s” in the diagram, and writes that “The rapidity of vibration in this instrument is extreme, so much that the shocks, which are coincident with the vibrations, produce no separate impression, but only a general numbness, when it is at its greatest speed.
The shocking device was invented by Charles Grafton Page (1812-1868, Ref. 3) who is usually regarded as the first electrical inventor in the United States, and, along with Nicholas Callan (1799-1864), is regarded as the developer of the induction coil. Both Callan and Page based their work on the 1831 observation by Michael Faraday that a changing current in a coil of wire would induce an EMF in a nearby coil. In Faraday’s experiments the two coils were wound side by side on the same piece of iron, but by the late 1830s the familiar technique of winding one coil over the other atop an iron core was established.
Page published his design in an 1838 paper in the American Journal of Science (Ref. 4). Thirty years later, just before his death in 1868, Page patented many of his designs and wrote a book about his work (Ref. 5). Figure 4 is taken from the patent papers (No. 76,654, granted April 14, 1868) and shows, on the left-hand side, his Double Helix with Vibrating Electrotome, and on the right is the Compound Magnet and Electrotome. An example of the latter instrument, built by
Daniel Davis and illustrated in the 1842 Manual of Magnetism is shown in Figure 5. Here the problem of the make-and-break contact is solved by using a soft-iron slug that is attracted to the core when it is energized, and, in the process, lifts the contact wire out of the right-hand mercury cup. This example is in the Smithsonian Collection.
In late January 1975 I had a telephone conversation with Deborah Warner of the Smithsonian who was calling around to various colleges urging them to hang onto their older pieces of apparatus, or donate them to the Smithsonian for safekeeping. We talked for a long time about our apparatus at Kenyon and she suggested that I might apply for a small grant from the Smithsonian to come and work there for a short time. March, and Spring Break came, and I was on the fifth floor of what became the National Museum of American History, photocopying Daniel Davis catalogues in the library and photographing Davis apparatus. One day Robert Post visited the Smithsonian, gave me a copy of his new book on Page (Ref. 6), and wrote on the flyleaf “For Tom/Fellow Friend of Daniel Davis/Bob.” I am still a friend of Daniel Davis (and Charles Grafton Page).
- The 1860 Ritchie catalogue that I photocopied at the Smithsonian has, at the top of the title page, “Ritchie’s/Illustrated Catalogue/of/Philosopical Instruments/and/School Apparatus” and at the bottom of the page, “Rooms, 313 Washington Street/BOSTON”. The 1869 catalogue says “Ritchie’s/Illustrated Catalogue/of/School Apparatus/BOSTON/147 Tremont Street/1869”.
- An Electrotome is a device for making and breaking an electrical circuit. Some may be built into the apparatus, as in the apparatus in Figs. 2, 5 and 6. The apparatus in Figs. 1 and 3 uses a separate electrotome that is placed on the same base as the coils. Page and Callan also designed free-standing electrotomes.
- Readers are also referred to Roger Sherman, “Charles Page, Daniel Davis, and Their Electromagnetic Apparatus”, Rittenhouse, Vol. 2, # 6: 34-47]
- Charles G. Page, “Magnetic Electrepeter and Electrotome, to be used with flat spirals”, Am.J.Sci, 35, 1839, p.112-113.
- Charles G. Page, “The American Claim to the Induction coil and its Electrostatic Developments”, (Intelligencer Printing House, Washington, 1867).
- Robert Charles Post, Physics, Patents & Politics; a Biography of Charles Grafton Page, (Science History Publications, New York, 1976).