Abstract
THE recent appearance of solar and lunar halos, parhelia, and paraselene, has called forth a considerable amount of correspondence from all parts of the country, and the accompanying figure may be taken as a composite representation of the solar phenomenon observed. A glance at the times at which the halos were observed on the 29th ult., makes it apparent that they occurred earliest in places of highest latitudes. At Driffield, in lat. 54°, the halo, with its attendant parhelia, was observed at 1.34 p.m., and the whole phenomenon disappeared at 2.8 p.m.; at Burton-on-Trent, lat. 52° 48′, the halos and parhelia were first observed at 2 p.m., and lasted more or less distinctly until 3 p.m.; whilst about a degree south of this, at Oxford, Colnbrook, and Walton-on-Thames, the phenomena occurred from about 3·30 to 4·30. The uniform difference in the times when the halos were observed at the places of different latitudes necessarily follows from the fact that they are formed by the action upon solar rays of prismatic crystals of ice suspended in the air by the ascending currents which especially occur in the spring and autumn. Those prisms that are in such positions that the rays from the sun in transmission through them suffer minimum deviation are the cause of the formation of halos, and since the angular distance of the sun equal to minimum deviation is about 22° this must be the radius of the halo, and the external circle, being produced by two such refractions in succession, has a radius of about 46°.
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Solar Halos and Parhelia. Nature 41, 330–331 (1890). https://doi.org/10.1038/041330a0
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DOI: https://doi.org/10.1038/041330a0