184 C. F. GAUSS ON THE GENERAL THEORY OF 



Article V. 



General Theory of Terrestrial Magnetism. By Professor 

 Carl Friebrich Gauss, of the University of Gottingen, 



[Translated by Mrs. Sabine, and revised by Sir John Herschel, Bart.] 



The unwearied zeal with which, in recent times, endeavours 

 have been made to examine the direction and intensity of the mag- 

 netic force of the earth, at all parts of its surface, is the more 

 worthy of admiration, as it has been prompted by the pure love 

 of science. Great as is the importance to navigation of the most 

 complete attainable knowledge of the lines of declination, more 

 than this is scarcely required for its purposes. Whilst science 

 dehghts to render such useful services, her own requisitions have 

 a wider scope, and make it necessary that equal efforts should be 

 devoted to the examination of all the magnetic elements. 



It has been customary to represent the results of magnetic 

 observations by three systems of lines, usually termed Iso- 

 gonic. Isoclinal, and Isodynamic lines. In course of time these 

 lines undergo considerable alterations both in position and in 

 figure, so that a drawing of them represents the phaenomena 

 correctly only for the epoch to which it corresponds. Hal- 

 ley's Chart of Dechnation for 170O is very different from that of 

 Bai-low for 1833; and abeady Hansteen's Dip Chart for 178O 

 differs greatly from the present position of the Isoclinal Unes. 

 Doubtless, in course of time, similar alterations in the lines of 

 intensity will be manifested ; but observations of this nature are 

 altogether too recent to furnish such indications at present. 



In all these maps there exist spaces either blank, or in which 

 the lines are but indifferently supported by observation. The 

 inaccessibility of parts of the earth's surface renders perfection in 

 this respect impossible ; but a rapid progress towards it may be 

 confidently hoped for. 



Viewed from the higher grounds of science even a complete 

 representation of the phaenomena after this manner is not itself 

 the final object sought. It is rather analogous to what the astro- 

 nomer has accomphshed, when, for example, he has observed the 

 apparent path of a comet in the heavens. Until the complicated 

 pheenomena have been brought in subjection to a common prin- 

 ciple, we have only building-stones, not an edifice. 



