98 



AKSEL S. STEEN. TERRESTRIAL MAGNETISM. [NORW. POL. EXP. 



OBSERVATIONS OF VIBRATION. 



The manner, mentioned on page 67, in which the time of vibration 

 for magnet V or VI was determined, gives, as will be understood, 11 separate 

 determinations for each series of vibrations, of the time for 100 vibrations, 

 all of which are given in the table. On rare occasions, the attempt to note 

 the moment of an expected passage of the magnet over the middle line of 

 the scale, has failed, and only 10, instead of 11, determinations of the time for 

 100 vibrations have been obtained. Once a series of observations of the 

 time for 101 vibrations has been made, twice of the time for 130, and once 

 of the time for 160 vibrations. Investigations as to the extent of the effect 

 produced by the proximity of the revolver upon the values for the hori- 

 zontal intensity deduced from the vibration observations, were made on the 

 20th April, 24th May, 4th and 26th July, and 20th August, 1895. On April 

 20th, the vibration box stood upon a stone slab frozen firmly into the ice. 

 During two series of vibrations with magnet V, and two with magnet VI, the 

 revolver lay east and west, 4 paces directly north of the magnet; while during 

 one series of vibrations with magnet V, and two with magnet VI, it was 

 laid aside. The values for the horizontal intensity, H, calculated from these 

 7 series of vibrations, are as follows: 



