Scientific memoirs : being experimental contributions to a knowledge of radiant energy / by John William Draper.

  • John William Draper
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Scientific memoirs : being experimental contributions to a knowledge of radiant energy / by John William Draper. Source: Wellcome Collection.

    387/488 (page 383)
    * Mkmoir XXVIIL] distribution OF HEAT IN THE SPECTRUM. 383 MEMOIR XXVIII. ON THE DISTRIBUTION OF HEAT IN THE SPECTRUM. From the American Journtvl of Science and Arts for 1872, Third Series, Vol. CIV., No. 161; Philosophical Magazine, August, 1872. Contents :—Early experiments seeming to prove that the maximum of heat is in the less refrangible spaces. — Comparison of the disiiersion and diffraction spectra.—Effect of compression in the less refrangible regions and of dilatation in the more refrangible.—Measure of heat in the two halves of the visible dispersion spectrum.—Description of the apparatus employed.—The different colored spaces are equally warm. Many ex^Derimenters, at vaiious times, have occupied themselves with the problem of the Distribution of Heat in the Spectrum. At fii-st it was supposed that there is a coincidence between the luminous and calorific radia- tions, and that the maximum of intensity in both occurs at the same point—that is, in the yellow space. This view was abandoned on the publication of the well- known experiments of Sir W. Herschel, who showed that in certain cases the maximum is below the red. Subse- quently Melloni, having discovered the singular heat- transparency of rock-salt, proved that when a prism of that substance is used, the maximum in question is as for below the red as the red is below the yellow; but that if the light has passed through flint-glass, the maximum ap- proaches the red; if through crown-glass, it passes into the red; if through water or alcohol, it enters the yellow. In the case of the sun's spectrum the distribution o^ heat was more closely examined by Professor Miiller, whose results in a general manner confirmed the views then held, that the invisible radiation below the red