In 1958 Hans Reichenbach’s second wife Maria Reichenbach and John Freund edited an English translation of the Philosophie der Raum-Zeit-Lehre [1]. The Philosophy of space and time [2] turned out to be one of the most influential books in the history of philosophy of physics. For those who never read the German original, it might come as a surprise that the English version is missing the translation of an Appendix entitled ‘Weyl’s Extension of Riemann’s Concept of Space and the Geometrical Interpretation of Electromagnetism.’ The Appendix covers around 50 pages of the German original, the Philosophie der Raum-Zeit-Lehre—not few considering that Reichenbach dedicated roughly 60 pages of the book to general relativity.

A translation of the Appendix was prepared in a nearly publishable form, and the typescript is preserved in the Reichenbach Archives in Pittsburgh (HR, 041-2101). However, the publication must have been withdrawn eventually. A reference to a no-longer-existing §46 on page 17 is the only clue of its existence. I have prepared a more readable TeX version of the translation that you can find here.

Reichenbach had discussed a first draft of the Appendix in correspondence with Einstein in 1926. I have reconstructed the episode in some details here. At that time, it was a widespread opinion that, after general relativity had successfully geometrized the gravitational field, the next obvious step was to ‘geometrize’ the electromagnetic field (see, e.g., [3] [4]). However, according to Reichenbach, this research program——the so called unified field theory-program——was based on a fundamental misunderstanding of the nature of Einstein’s geometrical interpretation of the gravitational field. To prove his point, Reichenbach put forward his own attempt of a geometrical interpretation of the electromagnetic field. Reichenbach’s geometrization is ultimately flawed, as Einstein and tried to explain in vain to Reichenbach in private correspondence. Nevertheless, Einstein ultimately agreed with Reichenbach’s message. As he wrote in the his review of the book: “In this chapter, [the Appendix] just like in the preceding—in my opinion quite rightly—it is argued that the claim that general relativity is an attempt to reduce physics to geometry is unfounded” [5].

If you are interested in a critical introduction to the Appendix you can find it here.

@book{Reichenbach1928,
  author       = {{Reichenbach}, Hans},
  title        = {Philosophie der Raum-Zeit-Lehre},
  date         = 1928,
  location     = {Berlin and Leipzig},
  publisher    = {Walter de Gruyter},
  hyphenation  = {german},
  addendum     = {\repr{Reichenbach1977}{\V{2}}}
}

@book{Reichenbach1958,
  author       = {{Reichenbach}, Hans},
  editor       = {{Reichenbach}, Maria},
  title        = {The Philosophy of Space and Time},
  date         = 1958,
  location     = {New York},
  publisher    = {Dover Publ.},
  hyphenation  = {english},
  translator   = {Maria {Reichenbach} and John Freund}
}

@sb{Weyl1918a,
  author       = {Weyl, Hermann},
  title        = {Gravitation und Elektrizit\"{a}t},
  date         = 1918,
  journaltitle = SBPAW,
  pages        = {465--480},
  hyphenation  = {german},
  month        = 5,
  addendum     = {\reprvd{Weyl1968}{2}{31}}
}

@article{Eddington1921,
  author       = {Eddington, Arthur Stanley},
  title        = {A Generalization of {W}eyl's Theory of the Electromagnetic and Gravitation fields},
  date         = 1921,
  journaltitle = {{Proceedings of the Royal Society London}},
  volume       = 99,
  pages        = {104--121},
  hyphenation  = {english},
  month        = 2
}

@article{Einstein1928d,
  author       = {Einstein, Albert},
  title        = {\rev{Reichenbach1928}},
  date         = 1928,
  journaltitle = {Deutsche Literaturzeitung},
  volume       = 49,
  number       = 1,
  pages        = {19--20},
  hyphenation  = {german}
}