royalsocietypublishing.org — 2026-10-04 (Investigator, Step I, first run)
Site: https://royalsocietypublishing.org (Royal Society journals; pre-1923 scans free to view)
Reached via Google queries: "Schuster" "Hemsalech" "constitution of the electric spark"; Royds 1908 "constitution of the electric spark" velocity Schuster Hemsalech Schenck; "Duration of luminosity of electric discharge in gases and vapours" 1913.
Findings
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The project document is confirmed as the Proceedings abstract. Proc. R. Soc. Lond. 64 (402-411): 331-336, DOI 10.1098/rspl.1898.0108 [web] https://royalsocietypublishing.org/doi/10.1098/rspl.1898.0108 (Google result listing; author given as "Arthur Schuster, Gustav Hemsalech").
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The full paper exists and is free to view: "VI. On the constitution of the electric spark", Phil. Trans. R. Soc. A 193 (1900), pp. 189-213, DOI 10.1098/rsta.1900.0006. [web] https://royalsocietypublishing.org/rsta/article/doi/10.1098/rsta.1900.0006/108275/VI-On-the-constitution-of-the-electric-spark. The landing page abstract repeats the opening of the Proc. abstract ("to measure this velocity of diffusion, with the special view of comparing different metals and different lines of the same metal"); the body is "only available via PDF" (scanned). Page range 189-213 is from Hemsalech's 1901 thesis citation (see archive.org notes) [web]. The project folder holds only the 6-page abstract; claims.md notes the abstract refers to "the tables given in the paper". This full paper is the main missing primary source (all metals' tables, the photographs, the calcium H and K observation reported by Royds). NOT downloaded: file downloads need the owner's explicit permission in this session; URL recorded for the owner.
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Follow-up by Schuster's own laboratory: T. Royds, "IX. The constitution of the electric spark", Phil. Trans. A 208 (1908), pp. 333-347, Plates 28-29, communicated by Schuster; received 29 Jan, read 13 Feb 1908. DOI 10.1098/rsta.1908.0023 [web] https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1908.0023 (page 1 read as image in Chrome PDF viewer). Royds (Beyer Fellow, Manchester) summarises the 1899 results in six points [web, page image p.333]: - (1) metal lines inclined on moving film, air lines straight; - (2) "They regarded the inclination of the lines as an indication of the velocity of propagation of the metallic vapour, and did not discuss any possibilities of the propagation of luminosity through vapour which may be, as a whole, stationary." - (3) different lines had different inclinations, "most marked in the bismuth spectrum"; - (4) "The lighter metals had a greater velocity than the heavier metals." (Note: claims.md item 5 says the abstract finds "no simple relation to atomic weight"; Royds' one-line summary reads the full paper more simply. Both stated; reviewers should compare against the Phil. Trans. text.) - (5) calcium H and K lines (impurity in silver electrodes) "became luminous first in the centre of the gap, and were propagated towards the electrodes" (not in the abstract; in the full paper); - (6) some vibration periods intense and short, others faint and persistent. Royds' table "Table I.—Velocities. Metal. Lines. Type of line." exists (Google snippet) but later pages could not be paged to in the viewer within the time limit. Not downloaded (permission). Bearing: Royds raises the alternative reading (moving luminosity through stationary vapour vs moving vapour) for claims 1, 2 and 4.
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R. J. Strutt, "Duration of luminosity of electric discharge in gases and vapours", Proc. R. Soc. A 88 (1913) 110-117, DOI 10.1098/rspa.1913.0013 [web] Google listing of https://royalsocietypublishing.org/doi/10.1098/rspa.1913.0013. Google snippet shows it cites "Schuster and Hemsalech, 'Phil. Trans.,' 1900, A, vol. 193, p. 189; Schenck, 'Astrophys. Journ.,' 1901, vol. 14, p. 116; Milner, 'Phil. Trans...'" and asks "Does the luminosity [persist after the discharge]". Direct page did not load in Chrome (tab error); not read. Bearing: afterglow duration bears on whether line slope measures vapour motion (claims 1, 2).
Result: positive. Recheck: yes (read Royds 1908 pp.334-347 and the 1900 Phil. Trans. paper in full once the owner permits download, or read in viewer).