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1848 __ The Aurora Borealis and the telegraph
Comment : Magnetized needles suffer disturbances in their normal direction which cause them to deviate generally from the west first, afterwards to the east. The current from the aurora borealis comes in waves which increase and decrease. Each wave is between 15 and 60 seconds. If one wave is positive, the next is negative, and so on. When the aurora is emitting a positive wave, the current on the line increases, and it neutralizes a battery totally when a negative wave is emitted. A man named Matteucci had the opportunity to observe the magnetic influence of the aurora borealis. During the appearance of the aurora borealis on November 17, 1848, the soft iron armatures employed in the electric telegraph between Florence and Pisa remained attached to their electro-magnets, as if the latter were powerfully magnetized, without, however, the apparatus being in action and without the currents in the battery being set in action. This singular effect ceased with the aurora, and the telegraph, as well as the batteries, could again operate without having suffered any alteration. In England, a man named Highton witnessed a strange event at the same time. The magnetized needle was always driven toward the same side, even with much force. (Patti Norton “The Aurora Borealis and the Telegraph”, Rainbow Riders Trading Post)M. Matteucci had the opportunity of observing this magnetic influence under a new and remarkable form. He saw, during the appearance of the aurora borealis of November 17, 1848, the soft iron armatures employed in the electric telegraph between Florence and Pisa remain attached to their electro-magnets, as if the latter were powerfully magnetized, without, however, the apparatus being in action, and without the currents in the battery being set in action. This singular effect ceases with the aurora, and the telegraph, as well as the batteries, could operate anew, without having suffered any alteration. Mr. Highton also ob- served in England a very decided action of the aurora borealis, November 17, 1848. The magnetized needle was always driven toward the same side, even with much force. But it is in our own country that the action of the aurora upon the telegraph- wires has been the most remarkable. (In “HISTORY, THEORY, AND PRACTICE OF THE ELECTRIC TELEGRAPH”. BY GEORGE B, PRESCOTT, SUPERINTENDENT OF ELECTRIC TELEGRAPH LINES. BOSTON: TICKNOR AND FIELDS, University Press, Cambridge, 1860, p. 317)
French comment : Sur un équivalent mécanique approximatif pour l'action de l'aurore boréale des 17 et 18 novembre 1848, par M. E. Highton [ingénieur télégraphique du London and North Western]Pendant cette aurore, le télégraphe électrique du tunnel de Watford a été violemment affecté, et durant plusieurs heures : le maximum de l'agitation a eu lieu à 3 heures du matin, le 18. Les fils du télégraphe s'étendent dans le tunnel sur un mille et 70 yards, et sont exposés à l'extérieur aux deux extrémités du tunnel sur une longueur de trois quarts de mille. Les indicateurs se sont souvent jetés d'un côté à l'autre pendant l'apparition et parfois sont restés infléchis d'une manière permanente pendant un temps considérable. Dans plusieurs occasions le courant électrique qui passait a été assez puissant pour attirer l'armature mobile de l'électro-aimant fixe d'un appareil à clochette, et faire ainsi marcher le signal. M. Highton a trouvé ensuite, par une expérience directe, qu'une pression d'un tiers d'once était nécessaire pour produire cet effet. Alors, par un calcul bien simple de la longueur et de l'épaisseur du fil, il a trouvé qu'il y avait aux deux extrémités 180 pieds superficiels d'exposés, et il en a conclu que le pouvoir de l'aurore étendu de même à une surface de un mille carré suffirait pour lever 75 tonneaux. Mais si on admet que le fil entier dans le tunnel s'est trouvé tout aussi bien affecté que celui exposé au dehors, alors il trouve que la force sur un mille carré dépasserait encore 31 tonneaux. (In "L'Institut - Journal Universel des Sciences", 1ère Section : Sciences Mathématiques, Physiques et Naturelles, Dix-huitième année, no. 844, 6 mars 1850, Paris, p. 80)
Urls : http://www.rainbowriderstradingpost.com/article1.html (last visited ) http://www.archive.org/stream/historytheorypra00presrich/historytheorypra00presrich_djvu.txt (last visited ) http://www.fullbooks.com/Atlantic-Monthly-Vol-IV-No-26-December4.html (last visited )

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