Abstract
THE accompanying figure on p. 490, represents a form of cloud which I have seen but twice in my life;* the first time about the commencement of June 1871, at five o'clock in the evening, at Washington, U.S.; the second at Beloit, Wisconsin, U.S, during the same year, and at the same hour. The state of the atmosphere presented similar meteorological conditions at both times, The appearances coincided with a north-west storm passing slowly north of the city without bursting, and disappearing in the south-east. Great branched masses of cloud appeared suspended from a sheet of Pallio-Cirrus. Some resembled bunches of grapes (a), others stalactites (b) in a striking manner, and still others formed round balls (c) separated by the azure of the sky. These balls seemed to be formed of snow flakes, and approached the form of Cirro-Cumulus; one might say of masses of snow rolled upon themselves by the effect of electric currents developed during the storm. This was accompanied by thunder and lightning at Washington, and by lightning only at Beloit. d represents one of these balls detached, with two sorts of penumbra, darker in e and f, and a streak at g, the rest whitish. Somebody at Beloit told me he had seen this form of cloud two or three times. A slightly brilliant aurora borealis was seen at Beloit the same evening. The night of its appearance at Washington no aurora was visible, but I do not know whether there may not have been one in other parts of and the next day at Beloit the temperature fell several degrees. It is a general belief that the aurora borealis is followed by a decrease of temperature. We know that in higher strata of the air vapour of water floats constantly in the form of frozen needles, especially in the polar regions. It is not impossible that these ice needles may be drifted by the electric current which engenders the aurora borealis* into lower latitudes, and thence towards lower strata of the atmosphere by the winds and storms. Hence the cooling of the air which is said to attend the aurora.
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POËY, A. On A New Form of Cloud* . Nature 4, 489–490 (1871). https://doi.org/10.1038/004489b0
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DOI: https://doi.org/10.1038/004489b0