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Central claims: SchusterAndHemsalech

Project note: one document only, "The Constitution of the Electric Spark" (Schuster and Hemsalech, Proc. Royal Society abstract, received 24 Jan 1899, read 2 Feb 1899). Text layer fully readable; no source gap. A deep read exists (deep/TheConstoftheElectSpark-4e82a8.md, pp.1-6, page images for p.3 and p.5); QE found no more needed. The document is only an abstract: the full 1900 paper (Phil. Trans. A 193, 189-213) with tables for Al, Mg, Bi, Cd, Hg and the photographs has not been read. This is a mainstream experimental physics paper, not a fringe claim. Claims 1-5 are [read] from that document; the Hull/Royds note in claim 2 comes from the Investigator's notes [web].

  1. Metal vapour torn from the electrodes of a spark crosses the gap at measurable speed: about 6e-6 s to reach the centre of a 1 cm gap for cadmium, with mean velocities of roughly 400-1500 m/s depending on metal and spectral line.
  2. A photographic film on a spinning disc (about 100 m/s) records metal spectral lines as inclined or curved while air lines stay straight, so line slope was taken by the authors to measure the motion of the emitting particles. (Later challenged: Hull 1906 on Doppler limits, Royds 1908; see the reviews.)
  3. The Leyden-jar discharge begins through air; the volatilised metal then carries the later oscillations, contrary to Feddersen's 1862 view that vapour takes no part in the discharge. Evidence offered: adding self-induction (a coil) makes the air lines nearly vanish.
  4. The vapour speed approximates the speed of sound in the metal vapour, V = 80 sqrt(T/rho), giving about 2700 K for cadmium (560 m/s, rho = 56) and implying the molecule in the spark is not much lighter than the normal vapour molecule.
  5. The abstract says aluminium and magnesium give higher molecular velocities, but that velocity has no simple relation to atomic weight (bismuth, measured with 2 jars, fast on some lines and slower on line 3793, aluminium over 3x zinc, zinc equal to cadmium), and different lines of one metal may give different velocities; the authors flag this last point and a counter-intuitive fall of velocity with capacity at short gaps as unsettled.