50 AKSEL S. STEEN. [2nd arc. exp. fram 



OBSERVATION OF VIBRATION. 



Magnet Y or VI was hung by a silk fibre in the suspension-tube of 

 the vibration-box, after its torsion had been, as far as possible, an- 

 nulled by means of a torsion balance. The pointed end of the magnet 

 moved during the vibrations over a linear scale, where the distance 

 between the division marks was 2.22° in angular measurement. 



Every third time the point of the magnet passed the middle divi- 

 sion on the scale, the moment was noted by the chronometer, from the 

 1st to the 31st passage inclusive, and then ordinarily from the 61st 

 to the 91st inclusive. Thus 11 determinations of the duration of 60 

 vibrations were obtained. In the period of repose, halfway between the 

 two halves of the vibration series, the amplitude was read on each side 

 of the central division on the scale, and the temperature from the ther- 

 mometer in the vibration-box. 



The hour given in the table is the mean of the hours noted for 

 the first and last passage of the magnet, reduced to local time. 



T = the observed time of vibration. 



A = the mean amplitude of the point of the magnet, from the 

 middle division of the scale. 



t == the temperature read. 



Q = logarithmic correction for the rate of the chronometer. 



a = logarithmic correction for the arc of vibration. 



T = correction to be added to log T for reduction to 0° C. according 

 to formula (4), p. 29. 



As no torsion determinations were made, there has been no oppor- 

 tunity of introducing any correction for torsion. 



