Annals of the Astrophysical Observatory of the Smithsonian Institution (1900)
Washington : Government printing office · leaf 287
Astrophysical Observatory Annals, Volume I. Plate XXV Normal Map of the Infra-reo Solar Spectrum, from Bolographic Investigation. Observations of S. 1‘. Langley, with the assistance of C. G. Abbot.
Infrared spectra · Solar radiation
Internet Archive · Smithsonian Libraries · Public domain (published before 1931). Free to use for anything.
![An illustration from Ioannis Padvanii Veronensis Opvs de compositione et vsv multiformium horologiorum solarium pro diuersis mundi regionibus : idq[ue] vbique locorum tam in superficie plana horizontali, quam murali quorsumcumq[ue] exposita sit, pertractans : nvper brevissimis ac facillimis doctrinis ab eo excogitatis luculenter traditum (1570)](https://img.insideoutlibrary.com/img/200/ia-ioannispadvaniiv00padu-32-0.webp)
![An illustration from The principles of harmony and contrast of colours [electronic resource] : and their applications to the arts (1890)](https://img.insideoutlibrary.com/img/200/ia-b21285676-553-0.webp)
