Wildly rainbow-hued plates from “Les Phénomènes de la Physique” and “Le Monde Physique,” physics textbooks written by Amédée Guillemin and published in 1868 and 1882.

"Polychromatic Fringes,” (detail). Plate VI in “Les Phénomènes de la Physique.” 1868.
“Polychromatic Fringes,” (detail). Plate VI in “Les Phénomènes de la Physique.” 1868. Mezzotint with watercolor by René Henri Digeon, after an image by J. Silberman. Wellcome Collection, London. Cc0 License 1.0. via https://publicdomainreview.org/collections/optics-illustrations-from-the-physics-textbooks-of-amedee-guillemin-1868-1882/
"Franges monochromatiques phénomènes d'interference diffractions par petit ouvertures"  (detail).
“Franges monochromatiques phénomènes d’interference diffractions par petit ouvertures” (detail). 1883. Mezzotint with watercolor made by M. Rapine after B. Desgoffe. Wellcome Collection, London. Cc0 Licence 1.0. via https://wellcomecollection.org/works/vphw3ezq
“Spectra of various light sources, solar, stellar, metallic, gaseous, electric." Plate IV in "Les phénomènes de la physique." 1868.
“Spectra of various light sources, solar, stellar, metallic, gaseous, electric.” Plate IV in “Les phénomènes de la physique.” 1868. Colored process print by René Henri Digeon. Wellcome Collection, London. Cc0 License 1.0. via https://publicdomainreview.org/collections/optics-illustrations-from-the-physics-textbooks-of-amedee-guillemin-1868-1882/
“Colour classification according to Mr. Chevreul’s system," Plate II in "Les phénomènes de la physique." 1868.
“Colour classification according to Mr. Chevreul’s system,” Plate II in “Les phénomènes de la physique.” 1868. Print made by René Henri Digeon, after an image by M. E. Chevreul. Wellcome Collection, London Cc0 License 1.0. via https://publicdomainreview.org/collections/optics-illustrations-from-the-physics-textbooks-of-amedee-guillemin-1868-1882/
“Soap bubble," Plate VI in "Le Monde Physique." 1882.
“Soap bubble,” Plate VI in “Le Monde Physique.” 1882. Mezzotint by M. Rapine, after an image by Alexandre-Blaise Desgoffe. Wellcome Collection, London. Cc0 License 1.0. via https://publicdomainreview.org/collections/optics-illustrations-from-the-physics-textbooks-of-amedee-guillemin-1868-1882/