RankingsPrimerArbiterPhysicistMathematicianContrarianQESites logClaimsSourcesResearch notes

2026-10-04 Internet Archive (archive.org)

Chrome was refused page-read permission on archive.org ("Permission denied for reading page content on this domain"), so the archive.org advancedsearch/metadata API and file downloads were run with curl (fallback).

Queries

  • advancedsearch: creator:(Kennard) AND (title:unipolar OR title:induction OR title:dielectrics OR title:aether) returned 1 irrelevant hit
  • title:(unipolar induction): 4 hits, none historical (Hraskó arXiv 0803.3616 "Unipolar Induction", 2010; NASA NTRS 1972 magnetosphere)
  • title:(effect of dielectrics on unipolar), title:(Kennard) AND title:(rotating): 0
  • title:(philosophical magazine) AND date:1912: did not find the 6th-series volume
  • metadata for identifiers londonedinburg6231912lond (Phil. Mag. 6th ser. v.23, Jan-June 1912) and londonedinburg6331917lond (6th ser. v.33, Jan-June 1917), guessed from the Wikimedia Commons filename: both exist

Findings (all [web])

  1. Kennard 1912, "XCIII. Unipolar Induction", Phil. Mag. (6) 23, 937-941: full text from the djvu OCR of https://archive.org/details/londonedinburg6231912lond, saved as files/Kennard-1912-PhilMag-23-937-Unipolar-Induction_IA-OCR.txt. Key content: - "Communicated by Prof. J. S. Townsend, F.R.S." The acknowledgement thanks Townsend for "assistance and advice". This was Oxford work: Kennard was a Rhodes scholar, B.S. Oxford 1911 (see AIP note). - Apparatus: steel bar 2 ft long and 2 in diameter, rotated by motor inside a stationary magnetising solenoid. An earthed metal case around the solenoid (the "inner cylinder", 7.3 cm diameter) and an insulated outer cylinder 49 cm long and 20 cm diameter are connected to a quadrant electrometer (about 850 divisions/volt). - It states both theories: moving force-line E' = E + (1/c)[V'H], with V' relative to the magnet, against Lorentz E' = E + (1/c)[VB], with V relative to the aether. Already in 1912 Kennard notes that under the moving-line theory "the vector E' in general fails to satisfy Laplace's Equation", the argument he develops in 1917 §7. - Result: 3 series, 70 observations; "+0.65 ±0.34 (probable error) and -0.7 ±0.35; mean, 0.0 ±0.24" divisions. Predicted under the moving-line theory: "probably about 37.0 divisions, pretty certainly greater than 31.0, and could not have been less than 26.0" (N max 350,000 CGS, about 72 rev/s, potential up to about 0.25 V). - Conclusion: "a rotating magnet does not 'carry its force lines' around with it ... electromagnetic induction caused by motion depends on absolute motion--that is, on motion relative to the ether". He limits it himself: "the method is not capable of distinguishing ... between the theories of Lorentz and of Hertz", and "a further investigation by another method, which is now under way" (this became the 1917 paper).
  2. Kennard 1917 full volume OCR (londonedinburg6331917lond): a second, cleaner OCR of pp.179-190, saved as files/Kennard-1917-PhilMag-33-179-IA-OCR.txt. It covers pp.188-190 (§7 rebuttal, §8 conclusion), which the deep read did not, with readable equations: f = (1/c)[V x B] + e + E; div(Kf) = 4πρ; "in free ether div E = 0. Hence in free ether div f = (1/c) div[V x B], and may not vanish". Also "the ether cannot be treated as only a particular species of the genus 'dielectric,' but must be regarded as complementary to all material dielectrics ... free ether has no such means of self-defence, and consequently all forces acting on it must themselves be solenoidal." §8 adds the gyrocompass analogy: "the effect is due to an absolute rotation in the same sense in which the operation of a gyrocompass is due to an absolute rotation of the earth". He also says "Rotation relative to the earth might in some unknown way be responsible for the observed effect, but this seems improbable." He calls the result "perhaps, the only low-frequency phenomenon which cannot easily be described in terms of 'action at a distance' between electrons and atoms". The volume index lists him as "Kennard (Prof. E. H.)".
  3. crossref-pre-1923-scholarly-works PDFs downloaded to files/: - Barnett-1912-PhysRevI-35-323.pdf: S. J. Barnett, "On Electromagnetic Induction and Relative Motion", Phys. Rev. (I) 35, 323 (1912). A footnote calls Kennard's 1912 paper "also ... based on incorrect theory" and "inconclusive". This is Barnett's characterization; he was Kennard's direct rival in this dispute. - Barnett-1913-PhysRev-2-323.pdf: Barnett, "On Electromagnetic Induction", Phys. Rev. 2, 323 (1913). It says Kennard "has now published three articles in reply, the last in the May number of this journal" and that "Mr. Kennard's fallacies are quite apparent to anyone familiar with this part of electrical theory" (Barnett's characterization). His substantive objection: in Kennard's 1912 experiment "the iron core ... rotated alone while the magnetizing coil remained fixed", so "it is quite impossible to say what fraction of the lines ... would adhere to the iron and move". He also argues that for steady fields "Lorentz's theory and Hertz's theory and Maxwell's theory are completely identical", and that Kennard "assumes, without justification, that div E = 0". - AIEE-1919-report-electromagnetic-induction.pdf: Barnett, "A Report on Electromagnetic Induction", Trans. AIEE 1919 (joint AIEE/APS meeting, Philadelphia, 10 Oct 1919). §23 says the "corollary of my experiments has been confirmed in each of two recent investigations; one by Kennard, who had done earlier work in this field; and one by Pegram ... the condenser and coil were both made to rotate. The condenser was found to become charged". He then says these experiments "prove either (1) that the ether does not exist and that the tubes of induction do not move, or (2) that the ether exists". Footnote 20 credits Kennard (Phys. Zeit. 13, 1912, p.1156) with first calling attention in print to a result Barnett "had previously made use of".
  4. Also seen but not downloaded: "Electromagnetism And Relativity" (Digital Library of India scan 2015.147975, which mentions "Kennard and Pegram"). The book's author was not checked (possibly E. G. Cullwick 1957, [memory] low confidence). URL: https://ia801505.us.archive.org/2/items/in.ernet.dli.2015.147975/2015.147975.Electromagnetism-And-Relativity_text.pdf