24 GAUSS AND WEBER ON TERRESTRIAL MAGNETISM. 



Cassel, Copenhagen, Dublin, Freiberg, Gottingen, Greenwich, 

 Halle, Kassan, Cracow, Leipzig, Milan, Marburg, Munich, Na- 

 ples, St. Petersburg, and Upsala. From eight of these places 

 no observations have yet come to our knowledge ; and, in some 

 others, the participation in the observations, from extrinsic cir- 

 cumstances, has not hitherto been uninterrupted and regular. 



Some terms of the earlier period of the Association have been 

 pubUshed in graphic representations in Schumacher's Astrono- 

 mische Nachrichten, and in PoggendorfF's Annalen der Physik. 

 The participation having so much increased, the time appeared 

 to have arrived for taking into consideration a regular publi- 

 cation, in order that the abundant collection of fruitful facts 

 might be made the common property of that portion of the public 

 which is interested in these researches. What we now offer may 

 be considered as the first annual report since the Association has 

 attained a certain extent. From the year 1837, the results of each 

 term will be made pubUc as soon as they can be brought together 

 in a sufficiently perfect manner. 



The observations, and their graphical representation, will not 

 merely be accompanied by those explanations and remarks which 

 relate immediately to themselves ; but we shall likewise add other 

 memoirs, in which various subjects belonging to the wide field 

 of tei-restrial magnetism — the instruments, their use and mani- 

 pulation, and varioTis applications — will find a place. 



With regard to the immediate object of the labours of our As- 

 sociation, the variations of the magnetic Declination, I may be 

 allowed to add one more remark. If, as cannot be doubted, the 

 two other elements of the terrestrial magnetic force, the Inclina- 

 tion and the Intensity, are subject to similar changes, the question 

 may be asked, why such careful labour has been devoted to the 

 first element, in preference, and hitherto exclusively ? 



The knowledge of the variations and the disturbances of the 

 magnetic Declination possesses in fact a very great practical in- 

 terest. To the mariner, and the surveyor, it must be of consi- 

 derable importance to know the frequency and magnitude of the 

 disturbances to which the compass is liable, even were it only 

 to learn what degree of confidence he might place in its indi- 

 cations. For geodesical purposes the futin-e progress of these 

 inquiries may probably do much more. If it is once esta- 

 blished that the irregular disturbances are never, or very sel- 

 dom, merely local, — but that they constantly, or almost always. 



