4g REPORTON 



u = angle of deflection, corrected for torsion force of the suspending thread. 



P= a constant depending upon the distribution of magnetism in the deflecting 



and suspended magnets. 



m = magnetic moment of the deflecting or vibrating magnet. 

 X horizontal component of the earth's magnetic force. 



(P \ 

 1 -i ) 



/ 5\__>400+^ 



\ l ' y) ~ 5400 



where v = the angle, expressed in minutes of arc, through which the suspended 

 magnet is deflected by a twist of 90 h- the suspension thread. 



m 



= r' tent* 



m __ m' / 

 X~ X'\ 



m 



In order to facilitate the finding of log. tan M, in the reduction of observations 

 of deflection, the following table has been prepared. With the argument log. u 

 (u being expressed in minutes of arc) it gives the quantity (log. tan u log. ), 

 of, in other words, the quantity which it is necessary to add to log. u in order to 

 obtain log. tan u. The arrangement of the table is such that the quantity (log. 

 tan u log. 7t) is to be added to the log. u on the same line with it, or to any 

 other log. u less than the one on the line next below. For example, if it were 

 required to find log. tan u corresponding to any log. u from 8.0000 to 1.4340, it 

 would only be necessary to add 6.46373 to the given log. u. 



