GAUSS AND WEBER OX TERRESTRIAL. MAGNETISM. 23 



smaller dimensions for Berlin. M. Sartorius observed with his in- 

 strument during all the terms when circumstances allowed, viz. 

 in June at Frankfort, and in September at Bramberg, in the 

 province of Salzburg. Observations were also made in Leipzig^ 

 Copenhagen, and Bi'unswiclc, with instruments exactly resem- 

 bling those of Gottingen. The result of the corresponding obser- 

 vations was quite similar to that above mentioned of the May- 

 term. Almost all the numerous movements obseiwed at Got- 

 tingen occurred in the observations at other places, and although 

 in varied relative magnitudes, yet with a concordance which did 

 not admit of mistake. 



In order to obtain further undeniable proof respecting this 

 remarkable result. Professor Weber, being then at Leipzig, ar- 

 ranged that corresponding observations should be made at that 

 place and at Gottingen, and certain hours of the forenoon, noon, 

 and evening of the 1st and 2nd of October were fixed upon for 

 the purpose. These observations, made by highly experienced 

 observers, and with the greatest care, were published entire 

 in Poggendoi-iF's Annalen der Physik, vol. xxxiii. p. 426, and 

 elucidated by graphic representations. The necessity now be- 

 came evident of observing the phaenomena at much shorter 

 intervals than Humboldt had chosen. We observed during 

 some of the appointed terms at intervals of tln-ee minutes, and 

 some other observers did the same. As, however, several of 

 the cooperatoi's adhered to the five minute intervals, and as these 

 in ordinary cases fully suffice, we subsequently, for the sake 

 of uniformity, adopted this as a general rule. But as such 

 small intervals render the labour incomparably more trou- 

 blesome than the noting from hour to hour, especially in cases 

 in which only a small number of persons can take part, it was 

 necessary, in order to ensure the stability of the Association, to 

 diminish both the number, and the duration of the terms. The 

 number has since been fixed at six in a year, and the duration of 

 each term at twenty-four hours. To each principal terra two 

 subordinate terms were added. Other details will be found in 

 the sequel. 



The observations have continued uninten'uptedly, according 

 to this plan, at Gottingen, and also at a constantly increa- 

 sing number of other stations. Apparatus of the same or of 

 similar construction to those in Gottingen, are employed in Al- 

 tona, Augsburg, Berlin, Bonn, Brunswick, Breda, Breslau, 



