OF ARTS AND SCIENCES. 283 



of Humboldt, a general awakening upon this subject tbroughout Europe 

 and America. 



In 1811 the Royal Danish Academy of Sciences in Copenhagen 

 offered their customary prize for the best answer to this question : 

 " Is it necessary, in order to explain the facts in the earth's magnetism, 

 to suppose more than one magnetic axis in the earth ? " In the follow- 

 ing year the prize was given to Hansteen. In 1814 he was appointed 

 to the Chair of Astronomy and Applied Mathematics in the University 

 of Christiania, recently founded by Frederick IV. of Norway. In 1819 

 he published, at the expense of the king, his greatest work, entitled 

 " Untersuchungen iiber den Magnetismus der Erde," in a quarto vol- 

 ume of 650 pages, illustrated by five copper-plates and an atlas of seven 

 magnetic charts. This book is the rich depository of all the observa- 

 tions which had been made on the elements of the earth's magnetism 

 prior to the date of its publication, and contains a condensed history 

 of the subject for that long j)eriod. But this was only preparatory to 

 its principal object, which was a mathematical analysis of all the obser- 

 vations in the light of Euler's theory of magnets. In this way Han- 

 steen labored to test the speculations of Halley as to the existence of 

 four magnetic poles in the earth, and to give a satisfactory answer to 

 the critical problem presented by the Danish Academy of Sciences. 

 After only a portion of the work was written and communicated to the 

 Secretary of the Academy, the prize was won. 



The declination-chart for 1787, prepared by Hansteen for his Mag- 

 netic Atlas, surpassed in accuracy and fulness similar charts already 

 published by Halley, by Mountain and Dodson, and by Churchman. 

 From the convergency of the lines of declination, Hansteen decided in 

 favor of two magnetic poles in the northern and also two in the south- 

 ern hemisphere. From the secular changes in these lines, he inferred 

 that the northern magnetic poles were moving obliquely towards the 

 east, and those in the south towards the west. Imperfect observations 

 enabled him to calculate approximately the period of complete revolu- 

 tion for each pole, and he called attention to this coincidence : that the 

 shortest time in which all the poles will return to the same relative 

 position agreed closely with the period of revolution in the precession 

 of the equinoxes. 



No one knew better than Hansteen that the magnetic observations 

 made, in 1768 and 1769, in Northern Asia, by those who were sent 

 there to watch the transit of Venus, reinforced by those collected by 

 Schubert in his journey to Siberia in 1805, were altogether insufficient 

 to mark the exact position of the Asiatic pole of magnetism. By the 



