smaller dimensions for Berlin. M. Sartorius observed with his instrument 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 Brunswick, with instruments exactly resembling those of Göttingen. The result of the corresponding observations was quite similar to that above mentioned of the May term. Almost all the numerous movements observed at Göttingen 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, arranged that corresponding observations should be made at that place and at Göttingen, 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 Poggendorff's Annalen der Physik, vol. xxxiii. p. 426, and elucidated by graphic representations. The necessity now became evident of observing the phænomena at much shorter intervals than Humboldt had chosen. We observed during some of the appointed terms at intervals of three minutes, and some other observers did the same. As, however, several of the cooperators 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 troublesome 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 term two subordinate terms were added. Other details will be found in the sequel.
The observations have continued uninterruptedly, according to this plan, at Göttingen, and also at a constantly increasing number of other stations. Apparatus of the same or of similar construction to those in Göttingen, are employed in Altona, Augsburg, Berlin, Bonn, Brunswick, Breda, Breslau,
