Meteorological essays / by François Arago ... with an introduction, by Baron Alexander von Humboldt. Tr. under the superintendence of Colonel Sabine.

  • François Arago
Date:
1855
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Licence: Public Domain Mark

Credit: Meteorological essays / by François Arago ... with an introduction, by Baron Alexander von Humboldt. Tr. under the superintendence of Colonel Sabine. Source: Wellcome Collection.

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    from tlie siimmits of its mountains, during tlie finest montlis of spring and early summer, in 1839, while Arran itself enjoyed the pnrest air and most serene sky, the opposite shores (tlie coasts of Ayrshire and Renfrewshire) had constantly over them a band of thick vapours, like a long grey cloud rising 1° or 1^° above the horizon.” According to M. Cagigal, an aiirora borealis was observed at Caracas on the 23rd of May, 1840. He remarks that although there hâve been some rare instances of this phenomenon having been observed at Cuba and at St. Domingo, he does not think that there is any other known example of its occurrence in so low a latitude as that of Caracas. M. Wartmann lias written to me from Geneva, that the periodical aurora of the 18th of October again showed itself very evidently on the 18th of October, 1841.* At Paris, MM. Laugier and Goujon saw a well-charac- terised aurora on the 12th of November, 1841, about half-past eleven. An aurora was also se en in France and Belgium, in the night between the 6th and 7th of May, 1843. Although it did not présent anything unusual, yet I will extract from the account sent to the Academy, details which, when compared with accounts from distant places, may perhaps lead to useful con- clusions. M. Quetelet wrote to me as foUows ; — During the daytime of the 6th of May, the march of the magnetometer had been very regular, and there was nothing to lead to the anticipation of the phenomenon which ivas to mani- fest itself in the evening. After ten o’clock, M. Beaulieu came to tell me, before he left for the night, that the needle showed a very sensible déviation, and I found it, indeed, in a state of extraordinary agitation. I wished to assure myself whether this dérangement did not coincide with some meteoroloo’ical * [It is singular that this historical summary should contain no mention of the remarkable aurora of the 25th of September, 1841, observed sirnul- taneously at Greenwich, at Toronto in Canada, and at Hobarton in Van Diemen Island, accompanied by disturbances of unusual magnitude in each of the three magnetic éléments, observed with appropria°te instruments at intervals of two minutes and a half for several hours, as well us at St. Hclena and at tlie Cape of Good Hope, where the magnetic disturbance prevailed, but no aurora was visible. The details of thèse observations, pub- lished shortly after the occurrence of the phenomena, were extensively cir- culated throughout Lurope and America, and attracted very general atten- tion.]—-En.