2 0 2 D O C . 1 2 3 T H E O R Y O F A F F I N E F I E L D Published in Nature 112 (1923): 448–449 on 22 September 1923. [1]The document is an English translation by Robert Lawson of the preceding document. [2]Einstein was awarded foreign membership of the Royal Society on 5 May 1921 (see Vol. 12, Calendar). [3]Eddington 1921, 1923. The following presentation of the theory is based on Einstein 1923e (Vol. 13, Doc. 425) and Einstein 1923h, 1923n, and 1925a (Docs. 13, 52, and 282, respectively). [4]Tullio Levi-Civita Hermann Weyl Arthur S. Eddington. [5]Droste’s contribution is acknowledged in a footnote added in proof to Einstein 1923n (Doc. 52).