Cassel, Copenhagen, Dublin, Freiberg, Göttingen, Greenwich, Halle, Kassan, Cracow, Leipzig, Milan, Marburg, Munich, Naples, 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 circumstances, has not hitherto been uninterrupted and regular.
Some terms of the earlier period of the Association have been published in graphic representations in Schumacher's Astronomische 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 publication, 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 public 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 terrestrial magnetism—the instruments, their use and manipulation, and various applications—will find a place.
With regard to the immediate object of the labours of our Association, 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 Inclination 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 interest. To the mariner, and the surveyor, it must be of considerable 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 indications. For geodesical purposes the future progress of these inquiries may probably do much more. If it is once established that the irregular disturbances are never, or very seldom, merely local,—but that they constantly, or almost always,
