PROGRESS IN MAGNETISM. 63 



in the first and brilliant suggestions of a theory of terrestrial 

 magnetism, which has been based by its founder, Friedrich 

 Gauss, upon strictly mathematical combinations. The means 

 which have led to these results are improvements in the in- 

 struments and methods employed ; scientific maritime expe- 

 ditions, which in number and magnitude have exceeded those 

 of any other century, and which have been carefully equipped 

 at the expense of their respective governments, and favored 

 by the happy choice both of the commanders and of the ob- 

 servers who have accompanied them ; and various expeditions 

 by land, which, having penetrated far into the interior of 

 continents, have been able to elucidate the phenomena of 

 terrestrial magnetism, and to establish a large number of 

 fixed stations situated in both hemispheres in corresponding 

 north and south latitudes, and often in almost opposite lon- 

 gitudes. These observatories, which are both magnetic and 

 meteorological, form, as it were, a net-work over the earth's 

 surface. By means of the ingenious combination of the ob- 

 servations which have been published at the national expense 

 in Russia and England, important and unexpected results 

 have been obtained. The establishment of a law regulating 

 the manifestation of force which is a proximate, although 

 not the ultimate, end of all investigations, has been satis- 

 factorily effected in many individual phases of the phenome- 

 non. All that has been discovered by means of physical ex- 

 periments concerning the relations which terrestrial magnet- 

 ism bears to excited electricity, to radiating heat and to light, 

 and all that we may assume in reference to the only lately 

 generalized phenomena of diamagnetism, and to that specific 

 property of atmospheric oxygen polarity opens, at all 

 events, the cheering prospect that we are drawing nearer to 

 the actual nature of the magnetic force. 



In order to justify the praise which we have generally ex- 

 pressed in reference to the magnetic labors of the first half 

 of our century, I will here, in accordance with the nature 

 and form of the present work, briefly enumerate the principal 

 sources of our information, arranging them in some cases 

 chronologically, and in others in groups. 5 * 



1803-1806. Krusenstern's voyage round the world (1812); 



* The dates with which the following table begins (as, for instance, 

 from 1803-1806) indicate the epoch of the observation, while the fig- 

 ures which are marked in parenthesis, and appended to the titles of 

 the works, indicate the date of their publication, which was frequently 

 much later. 



