Annals of the Astrophysical Observatory of the Smithsonian Institution (1900)
Washington : Government printing office · leaf 31
the slit. Two rock- salt lenses of 3.5 meters focus were used for collimator and objective, and the 60° prism was of rock salt 64 mm. on a side. The bolometer strip, 2 mm. wide, subtended 20' and the slit the same. A test of the selective absorption of rock salt for the rays in question was made by… … FIG. 5.- ROCK-SALT PRISMATIC SPECTRA. ALLEGHENY OBSERVATORY. The result of the investigation was to show that the heat from terrestrial sources, such as heated soil, is of a much longer wave-length than the major portion of that received from the sun, and that rising temperature in the source of…
Infrared spectra · Solar radiation
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