Abstract
London. Royal Society, November 7.—Sir Archibald Geikie, K.C.B., president, in the chair.—Louis V. King: The scattering and absorption of light in gaseous media, with applications to the intensity of sky radiation. The analysis of the present investigations seems to support the view that, at levels above Mount Wilson, molecular scattering is sufficient to account completely both for attenuation of solar radiation and for the intensity and quality of sky radiation. Even at sea-level the effect of “atmospheric dust” can be taken into account in a simple manner in formulae for absorption and scattering.—Dr. P. E. Shaw: A standard measuring machine.—E. M. Stubbs and Dr. E. B. R. Prideanx: A spectro-photometric comparison of the emissivity of solid and liquid gold at high temperatures with that of a full radiator. (1) The emissivity of solid and liquid gold at high temperatures, relative to the emissivity of a full radiator at the same temperatures, has been measured throughout the visible spectrum. (2) A sharp discontinuity in the emissivity takes place at the melting point, the liquid gold emitting more strongly than the solid in the red and yellow, and less in the extreme blue. The shape of the “relative emissivity” curves is quite different in the two cases. (3) The curve of “relative emissivity” of solid gold at high temperatures is similar to that of absorptivity at low temperatures as determined from reflectivity measurements; whether it is identical, in which case the temperature coefficient of the absorptivity would be nil, could not be absolutely determined, owing to the change of structure which a polished surface undergoes on heating. (4) No temperature coefficient of “relative emissivity” could be detected for the liquid metal through a range of more than ioo°. (5) “Black body” temperatures of solid and liquid gold at the melting point have been calculated. (6) It has been shown that the general equation expressing the radiation of a selective radiator is of the form
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Societies and Academies. . Nature 90, 349–351 (1912). https://doi.org/10.1038/090349a0
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DOI: https://doi.org/10.1038/090349a0