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36 had done, to the fact that the magnetic needle deflects, when a galvanic current comes near it.

Arago, of the Academy of Sciences in Paris, received the information about Oersted's doings at the same time, and from the same source as myself.

It was in August, 1820, at Geneva, when I was making preparations for my second ascent of Mont Blanc, in order to follow out observations on the effects of the rare air at great heights on muscular motion, when Professor August Pictet, with whom I was then in daily intercourse, received Oersted's circular announcement in Latin: "Experimenta circa effectum conflictus electrici in acum magneticum," dated Copenhagen, July 21st. Just then Arago had come to Geneva, being on his way to Paris, where he intended to observe the solar eclipse on the 7th September.

At Pictet's request, Professor de la Rive repeated Oersted's experiment several times, as well with a powerful battery of 380 pairs of plates six inches square, as with a small one, made by Selligue, of twelve copper cups with a zinc plate in each. It happened that on the 19th of August, when De la Rive was experimenting with the said large battery, to show Arago and some scientific persons of Geneva the brilliant incandescence of