  This article presents hitherto unpublished correspondence of Struble in 1947
with Menger, Chandrasekhar, and eventually Einstein, about a possible
observational test supporting Einstein's special relativity against Ritz's
emission theory using binary stars. This `Struble effect,' an acceleration
Doppler effect in emission theory, appears to have been overlooked, and the
historical context, including de Sitter's binary star test of special
relativity, is also discussed.
