Determine whether Russell showed a graphical H–R diagram at the 1913 Royal Astronomical Society meeting

Determine whether Henry Norris Russell showed a graphical equivalent of the stellar spectral-class and absolute-magnitude distribution during the June 1913 meeting of the Royal Astronomical Society in London.

Background

Henry Norris Russell presented an early version of his stellar diagram at a June 1913 meeting of the Royal Astronomical Society. A tabulation of stars by spectral class and absolute magnitude survives in connection with that visit, but the paper notes that no copy of the diagram itself has survived. The unresolved historical issue is whether Russell presented the tabulation alone or also displayed a graphical diagram at the meeting.

References

Although no copy of the diagram shown on that occasion has survived, we know that during his visit he met J. Norman Lockyer (1836–1920), who was developing his own ideas on stellar evolution. Russell evidently showed Lockyer the tabulation reproduced here as Figure 1, a copy of which was clipped to a note that Lockyer sent to Russell during the visit (11). Although presented as a table rather than a graph, its essential features are unmistakable: the distribution of stars by spectral class and absolute magnitude foreshadows the structure of Russell's later diagram. Whether this table, or a graphical equivalent, was also shown during the Royal Astronomical Society meeting is not known.

— Could John Ellard Gore have pre-empted the Hertzsprung-Russell diagram?  (2608.18799 - Shears, 19 Aug 2026) in Section “The emergence of the H-R diagram,” p. 4