(Berlin, Haude et Spener, 1770). 4to. No wrappers, as issued in ""Mémoires de l'Academie Royale des Sciences et Belles Lettres"", Année 1768, tome XXIV, pp. 70-79 a. pp. 80-108 a. Clean and fine.
First printing of both papers. In the paper on photometrics Lambert uses his photometric theories on the art of painting, and it has a long, remarkable discussion of the technics used by Leonardi da Vinci. - The first paper deals with the propagation of sound waves in different media.