635 



called in contradistinction to the regular periodical and secular varia- 

 tions) to a more close examination, by means of systematized ob- 

 servations made simultaneously in many parts of Germany. With this 

 view, six concerted days in each year were set apart in which the di- 

 rection of the declination-magnet should be observed with great 

 accuracy, by methods then for the first time introduced, at successive 

 intervals of five minutes for twenty-four consecutive hours ; the me- 

 teorological instruments being observed at the same time. The 

 clocks at all the stations were set to Gottingen mean time (Gottingen 

 being the birth-place of the Association), and the observations were 

 thus rendered strictly simultaneous throughout. The high respect 

 entertained for the eminent persons with whom the scheme of the 

 Association originated, obtained for it a very extensive cooperation, 

 not limited to Germany alone, but extending over a great part of the 

 European Continent. The observations of the "Term-days," as 

 they were called, were maintained until 1841, and were all trans- 

 mitted to Gottingen for coordination and comparison. 



The principal results of this great and admirably conducted co- 

 operative undertaking were published in works well known to mag- 

 neticians. They may be summed up as follows : The phenomena 

 which were the subjects of investigation were shown to be of casual 

 and not regular occurrence; to prevail contemporaneously everywhere 

 within the limits comprehended by the observations ; and to exhibit 

 a correspondence surprisingly great, not only in the larger, but even 

 in almost all the smaller oscillations ; so that, in the words of the 

 Reporters, MM. Gauss and Weber, " nothing in fact remained which 

 could justly be ascribed to local causes." 



Equally decided were the conclusions drawn against the previously 

 imagined connexion between the magnetic disturbances and derange- 

 ments of the atmosphere, or particular states of the weather. No 

 perceptible influence whatsoever on the needle appeared to be pro- 

 duced either by wind-storms or by thunder-storms, even when close 

 at hand. 



The correspondence in the simultaneous movements of the declina- 

 tion-magnet, so strikingly manifested over an area of such wide extent, 

 was however more remarkable in respect to the direction of a per- 

 turbation than to its amount. The disturbances at different stations, 

 and even, as was expressly stated, at all the stations, coincided, even 



VOL. X. 2 X 



