Abstract
IN reference to Mr. Ralph Abercrombie's letter (NATURE, vol. xxvii. p. 173), I may mention that his remarks quite accord with an opinion expressed to me by my friend, H. R. Procter, that the “aurora is generally formed in some imperfect mist or vapour.” I am intending sumac experiments on discharges in vacuo under such conditions and reduced temperatures, also on phosphorescence, in connection with which M. Lecoq de Boisbaudrau has shown in his “Spectres lumineux,” that we get a line in the red, brightening as the temperature is reduced. I do not read the result of my Swan lamp experiment, as Mr. Munro (same number and page) does. The lamp, when perfect, gave quite a bright white glow, with a strung carbon spectrum. I should therefore attribute the absence of the nitrogen spectrum at this time nut so much to a high spectrum as to the probability that the lamp had been, as far as possible, exhausted of air, and filled with some form of carbon gas. I am not aware of any air-vacuum point at which the nitrogen bands or lines disappear, except for want of light in the discharge. With regard to the letter of W. M. F. P. on the “Meteor of November 17th,” I only assumed the correctness of the figures and heights quoted in mine fur the purpose of showing the complex nature of the auroral questions. I am not the less perfectly satisfied that the “beam” was a true aurora, and not a meteor, my spectroscopic observation of it putting this beyond a doubt.
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CAPRON, J. The Aurora and its Spectrum. Nature 27, 198 (1882). https://doi.org/10.1038/027198c0
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DOI: https://doi.org/10.1038/027198c0
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