  Recently, the page-proof, with corrections, of Einstein's 1920 publication on
the "Propagation of Sound in Partly Dissociated Gases" was discovered in
Leiden. The last two pages of the proof are crossed out and replaced by a sheet
in Einstein's handwriting. In these notes, I briefly address the following two
questions: A) Concerning the page proof, what is the difference between the
contents of the crossed-out pages and the new page? B) Concerning the
publication, are Eqs. (18,21,22) correct?
