588 WEBER ON THE TERM-OBSERVATIONS AT ALTEN. 



made elsewhere are little or not at all adapted; in particular we 

 might, by their means, determine most securely whether the forces 

 which cause the variations have their seat above or below the sur- 

 face of the earth. Without this multiplication of stations in its 

 vicinity, observations of the variations at Alten will have a much 

 inferior value, as they diifer so greatly from those at the nearest 

 present station, Upsala, of which we may convince ourselves by 

 inspection of the curves of declination and horizontal intensity 

 on the 23rd of February, 1839, shown in Plate XXVI. The 

 three declination curves represent the variations of that element 

 from noon to 10 p.m., Gottingen mean time, at Alten, Upsala, 

 and Gottingen, and are all on the same scale. The two curves 

 of the horizontal intensity are for the same period, and repre- 

 sent the changes at Alten and at Gottingen, which was the 

 next most northern station at which the intensity was observed 

 during that term. We cannot perceive in the two latter curves 

 even that trace of resemblance which is visible in those of the 



declination. ,,r -r^r 



W. Weber, 



