I N T R O D U C T I O N T O V O L U M E 1 6 l x x i Eisenhart’s book Non-Riemannian Geometry (Doc. 279, Eisenhart 1927). In Feb- ruary 1929, Einstein apologized directly to Eisenhart for having “overlooked the fact that you and Weitzenböck, along with several others, had already treated telep- arallelism mathematically” (Doc. 394). Eisenhart’s book was indeed listed in Weitzenböck’s article. So was pertinent work by Giuseppe Vitali, to whom Einstein also had to send a note of apology (Doc. 407). The most embarrassing letter in this respect, however, must have been the one he received in May 1929 from Élie Cartan (Doc. 520). Very politely, Cartan pointed out that he, too, had already published a number of papers on teleparallel geometry. He even reminded Einstein that he had shown him “the most simple example of a Riemannian space with distant parallelism at Mr. Hadamard’s place,” when Einstein visited Paris in 1922. In his response, Einstein immediately accepted Cartan’s priority. What made things worse was that Weitzenböck, in compiling his “presumably complete” literature list, had “overlooked” Cartan’s work (Doc. 525). What Einstein apparently did not know was that this lapse was in no way accidental but likely an expression of Weitzenböck’s Francophobia. Indeed, in the preface to his 1923 textbook on invariant theory, he had hidden an acrostic, reading “Down with the French.”[49] Whether Cartan knew of this political background was left unmentioned in his reply (Doc. 531). He did point out, though, that Weitzenböck had very thoroughly cited works by Bortolotti, who in turn had referred to Cartan’s earlier work. Einstein realized that he needed to rectify the situation, but was “at a loss over how I should go about doing that in such a way that all the justifiable claims will be satisfied” (Doc. 525). At that time, Einstein had apparently just composed a “summary article” about the teleparallel approach that would treat the subject in some detail. He now suggested to Cartan that he should write a historical exposi- tion on teleparallel geometry, to be published back-to-back with Einstein’s paper, thus providing “a good example of how such priority questions can be dealt with in a respectful and sympathetic manner” (Doc. 525). Cartan accepted this proposal on 15 May (Doc. 531) and sent the manuscript of a historical note on 24 May (Doc. 536). Neither Einstein’s nor Cartan’s papers appeared as conceived, but eventually the plan materialized (Einstein1930x and Cartan 1930) and would lead to an in- tense correspondence between Cartan and Einstein, which, however, took place after the time period covered by this volume.[50]