EINSTEIN, ALBERT. - THE EQUIVALENCE PRINCIPLE.

Lichtsgeschwindigkeit und Statik des Gravitationsfeldes; (&) Zur Theorie des statischen Gravitationsfeldes;

(Leipzig, Barth),1912. 8vo. No wrappers. In: "Annalen der Physik IV, Bd. 38", No 7. Pp.249-472 a. 3 plates. (Entire issue offered). Einstein's papers: pp. 355-369 and pp. 443-458. Clean and fine.

Both papers in first edition, and they are considered as the first appearance of a Nonlinear Field Equation for Gravitation.
"Einstein published two remarkable memoirs in 1912 which were efforts to construct a complete theory of gravitation incorporating the equivalence principle. In these memoirs Einstein supposed that the gravitational field can be characterized completely by one function, the local speed of light, analogous to the Newtonian description, where only the gravitational potential appears. By an extraordinary argument he extended the potential equation of Newton...In his second Memoir in 1912, he used the equivalence principle to show the influence of a static gravitational field on electromagnetic and thermal processes." (DSB IV p.320 ff). - Weil No. 47 and 48.

Order-nr.: 49779