“…. Since the transition ( §2.1) from general relativity to Weyl's first gauge theory (1918, §2) has been amply discussed in Pais (1982), Vizgin (1984), Scholz ( , 1995Scholz ( , 2001aScholz ( , 2004Scholz ( , 2011b, Cao (1997), Hawkins (2000), Coleman & Korté (2001), Sigurdsson (2001), Ryckman (2003aRyckman ( ,b, 2005Ryckman ( , 2009, Penrose (2004) and Afriat (2009), I concentrate on the next step, which took Weyl to his second theory ( §3)-mainly determined by the new undulatory ontology ( §3.1) introduced by Louis de Broglie (1924), Dirac (1925), Schrödinger (1926) and others. Mainly but not wholly: Weyl had every reason to keep the electricity, gravity and abstract gauge structure of his first theory; but now with three ingredients (matter, electricity, gravity), three different gauge relations were possible, two of which (electricity-matter, electricity-gravity) were more plausible than the third (matter-gravity).…”