Page:Scientific Memoirs, Vol. 2 (1841).djvu/103

Rh Observatory of Göttingen, during the prevalence of the most violent storm. If any one, however, were inclined to infer from such experience, that storms in the atmosphere, on the other hand, counteract or enfeeble the magnetic forces, such an idea would be dispelled by what took place during the term of January 1836. During this term a very violent storm prevailed at Göttingen, and at many other stations; and several observers in other places accompanied the results which they communicated, by the expression of a fear that from this circumstance the unusually large movements shown by the magnetometer might offer but little accordance. Nevertheless, the harmony of the curves from the various stations was so complete (see the representations in Plate V.) that it might have been termed wonderful, if the same thing had not been manifested before by so many experiments. As with wind storms, so it is with thunder storms, which, even when close at hand, exercise (as attested by several cases which have occurred here and at other places) no perceptible influence on the magnetic needle.

A letter from M. von Humboldt, received in August, 1836, contained the information that, from the 10th to the 18th of August, the magnetic changes would be observed uninterruptedly every quarter of an hour at Reikiavik, in Iceland, by a practised French astronomer, M. Lottin, with Gambey's apparatus, and expressed the wish that corresponding observations might be made on one or on some of those days with magnetometers. In consequence an unusual term was fixed for the 17th and 18th of August, and as far as the shortness of the time allowed, several members of our Association at other stations were invited to take part in it. This unusual term was observed in Upsala, the Hague, Göttingen, Berlin, Leipzig, and Munich, in exactly the same way as the usual terms; and if the graphically represented observations in Plate VII. exhibit exceedingly interesting changes, we have only to regret that the place reserved at the top of the plate for the Iceland observations is vacant, as we have not been able to obtain the slightest information respecting the result of the French Icelandic observations.

The September term presents a case which may be noticed somewhat in detail, as it confirms, in a very instructive