4to (252 x 183 mm). 15 engraved folding plates by Phillipe Simonneau. (Some minor toning and spotting, slight offsetting from plates, a few plates toned.) Contemporary calf gilt, 2 brown morocco lettering-pieces gilt, edges red-dyed (some wear, joints starting to crack but holding firm). Provenance: Monsieur Langlois, Royal Engineer, Royal Academy of Science for Instruments of Mathematics (inscription). 

FIRST EDITION of de Mairan's studies of the aurora borealis around Paris. PRESENTATION COPY, INSCRIBED BY DORTOUS DE MAIRAN TO LANGLOIS: "À Monsieur Langlois Ingenieur du Roy et de l'Academie Royale des Sciences, pour les Instrumens de Mathématique, Par fon tres affectionné, et fidelle ami [D'Ortous de Mairan]." De Mairan hypothesized that the Northern Lights were caused by the atmosphere's interaction with zodiacal light, in contrast to the contemporary belief that aurora borealis was vapor emanating from the earth and catching flame.