Astronomie

First offprint in the original wrappers, of Einstein's important follow-up paper on the field equations in his General Theory of Relativity. - Contents: In present paper Einstein suggests a modification of his field equations to allow for stable elementary particles. According to Pais this text "may be considered Einstein's first attempt at a unified field theory"” (Pais, Subtle is the Lord, p. 287). - Condition: Cover at margins minimally dusty, otherwise very fine indeed, probably unread. - Rarity: According to Weil early offprints of Einstein’s papers may also be qualified as original and also highly collectable editions, however they were printed in a certain, but still small print run for commercial use (mainly to sell them to fellow natural scientists): „No doubt, the first appearance in a periodical is the „original edition“, but I have to leave it open for collectors, librarians and others to decide whether these offprints in wrappers, mostly with a printed title on them (especially in the »Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften«) are also „original editions“. These offprints are printed from the same setting as the text, but often with new pagination.“ (p. 4). Additionally to offprints like the present, some copies bearing the imprint „Überreicht vom Verfasser“ [Presented by the Author] ABPC (1973ff.) and JAP/APO (1950ff.) record only 1 copy of this edition at auction (2011). - Reference: Boni-Russ-L. 111; Collected Papers, vol. 7, 17; Schilpp 123; Weil 106.