‎"LORENTZ, H.A. & L. (LUDWIG VALENTIN) LORENZ - THE ""LORENZ-LORENTZ EQUATION""‎
‎Ueber die Beziehung zwischen der Fortpflanzungsgeschwindigkeit des Lichtes und der Körperdichte" Von H.A. Lorentz. (+) Ueber die Refractionsconstante" von L. Lorenz. (2 Papers).‎

‎Leipzig, Johann Ambrosius Barth, 1880. Without wrappers as issued in ""Annalen der Physik und Chemie. Hrsg.von G. Wiedemann."", Neue Folge Band IX, Heft 4. Titlepage to Bd. 9. Pp. 513-680 a. 1 folded engraved plate. + Neue Folge Band XI, Heft 9. Titlepage to Bd. 11. Pp. 1-176 a. 2 folded plates. Lorentz's paper"" pp. 641-665 (of Heft 4). Lorenz's paper: pp. 70-103. (2 entire issues offered). A stamp on titlepapges and verso. Both clean and fine.‎

Reference : 43412

‎First printing of these two fundamental papers, revealing a lasting result in the history of physics, as both authors INDEPENDENTLY OF EACH OTHER, discovered the mathematical formula for the dependence of refraction of light upon specific gravity. It is very interesting that they found the formula - now called the Lorenz-Lorentz Equation or Formula - with altogether different ways and methods. They both discovered the formula before 1880, L.V. Lorenz first, but, also independently, published their final versions in the same periodical, and in the same year (the 2 papers offered). - Parkinson ""Breakthroughs"" 1880 P.‎