Opuscula Varii Argumenti

Twelve folding engraved plates. 1 p.l., 300 pp.; 1 p.l., 166 pp.; 1 p.l., 165 pp. Three vols. in one. 4to, cont. sheep-backed mottled boards (minor rubbing, some foxing as is usual with this book). Berlin: A. Haude & J.C. Spener, 1746-50-51. First edition of one of Euler's scarcer works; this collection contains separate monographs on astronomy, optics, magnetism, electricity, mathematics, and physics and includes several of Euler's most important and fundamental works. Vol. I deals mostly with astronomy and optics. It is valuable for Euler's tables of the sun and moon and for his discussion of the problem of perturbations. Euler's studies in astronomy embraced a great variety of problems: determination of the orbits of comets and planets, calculation of the parallax of the sun, the physical nature of comets, celestial mechanics, etc. With regard to optics, Euler herein rejected the dominant corpuscular theory of light and constructed his own theory in which he attributed the cause of light to peculiar oscillations of ether. Vol. II is concerned with physics and mathematics. Topics examined here are the propagation of sound and light, analysis, the theory of differential equations, and ellipses. In Vol. III, "Euler adopts the Cartesian doctrine of pores and magnetic particles, magnetic matter is more subtile than the ether itself and is propagated through a magnet in one direction only, p. 10; declination and dip explained, p. 30."-Wheeler Gift Cat. 366. A very good set. Engraved bookplate of Canterzani. ❧ D.S.B., IV, pp. 467-84. Houzeau & Lancaster 3482. Sotheran, Supp., 2242-"Rare.".