GAUSS AND WEBER ON TERRESTRIAL MAGNETISM. 91 



Observatory of Gottlngen, 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 Janu- 

 ary 1836. During this term a very violent storm prevailed at 

 Gottingen, and at many other stations ; and several observ^ers in 

 other places accompanied the results which they communicated, 

 by the expression of a fear that from this circumstance the un- 

 usually large movements shown by the magnetometer might 

 offer but Uttle accordance. Nevertheless, the harmony of the 

 curves fi'om the various stations was so complete (see the repre- 

 sentations in Plate V.) that it might have been termed wonder- 

 ful, 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 occuiTcd here and at other places) no percep- 

 tible influence on the magnetic needle*. 



A letter from M. von Humboldt, received in August, 1 836, con- 

 tained the information that, from the 10th to the 18th of August, 

 the magnetic changes would be obsen-ed 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 obsen^ations might be 

 made on one or on some of those days with magnetometers. In 

 consequence an unusual term was fixed for the l7th and ISth 

 of August, and as far as the shortness of the time allowed, seve- 

 ral members of our Association at other stations were invited to 

 take part in it. This unusual term was observed in Upsala, 

 the Hague, Gottingen, Berlin, Leipzig, and Munich, in exactly 

 the same way as the usual terms ; and if the graphically re- 

 presented observations in Plate VII. exhibit exceedingly in- 

 teresting changes, we have only to regret that the place resented 

 at the top of the plate for the Iceland obsenations is vacant, as 

 we have not been able to obtain the slightest information re- 

 specting the result of the French Icelandic obsei-vations. 



The September term presents a case which may be noticed 

 somewhat in detail, as it confirms, in a very instructive man- 



* There is, of course, no question here of experiments in which the atmo- 

 spheric electricity is conducted to the earth by means of a conducting wire 

 passing through a multiplier surrounding the needle. 



