344 M. F. Kohlrausch on the Absolute Value of the 



M, without being displaced, was fixed in a rotating clamp, so 

 that it could be adjusted in an east and west direction. It 

 thereby acts upon a smaller needle (accessory needle) with a 

 mirror, which is suspended north and south to strings which 

 hang from a long brass rod to the top of the room. Half of 

 the distance of these from each other, the temperature being per- 

 ceptibly the same in the two determinations, was determined 

 once for all, and was found to be 



R= 1501*70 millimetres. 

 The correction-term with ^-, in consequence of the ratio of 



the length 1 : 2 of the principal bar to the accessory needle, is 

 brought almost to zero. By deflections from second distances 

 it was determined that the angle of deflection <j> at the distance 

 R was expressed by 



c onst. / 1030 0\ 



W\ R 2 ./" 



The distance of the mirror from the scale, the position of 

 which was always given by the unused string, amounted to 

 3015 millimetres. 



Ratio of torsion of the accessory needle =000241. 



If, finally, the mean position of the bifilar during the deflec- 

 tions be denoted by 5, we may put for the observed angle of de- 

 flection cf> 



tan O =1 (1 + 0*000105 . 8) tan <f>. 

 Then 



tan« = 



M 

 T„ 



1-00241 



1- 



10300 

 R 2 



R 3 tan (f> . 



Determinations of intensity were made on the 19th and 22nd 

 of August. The duration of the vibration was each time observed 

 at the beginning and at the end. There were obtained : — 





Duration, 

 r. 



Arc, 



Bifilar, 



d. 



Correction for 



*V 



oo small i m 

 arc. °" 



Aug. 19.... 



sec. 

 20-5709 

 20-5648 



diy. 

 282 

 205 



+3-5 



+ 8-9 



sec. 

 -0-0004 

 -0-0002 



sec. 

 +00038 

 +00096 



Mean = 



sec. 

 26-5743 

 20-5742 



= 20-5742 



Aug. 22. ... 



20-5793 

 20-5658 



220 

 246 



-1-5 

 +51 



-0-0002 

 -0 0003 



-00015 

 +00055 



20-5776 

 205710 













Mean = 



= 20 5743 



