BiFiLAR OR Horizontal Force Magnetometer. 



xli 



Table 6. — Observations of Deflection of the Balance Magnet suspended horizontally 

 by the Declinometer Thread, January 10, 1848. 



Distance of 



Deflecting 



Bar. 



Observed 

 Deflec- 

 tion. 



Mean 

 Observed 

 Deflec- 

 tion. 



Value of 

 1 + *. 



Deflection 

 Corrected 



for 

 Torsion. 



Value of 



One 

 Sc. Div. 



Resulting 

 Deflec- 

 tion. 



Temp, of 



Deflecting 



Bar. 



Feet. 



'•» { N. 



- { 1. 



Sc. Div. 



26-96 

 23-78 



56-83 

 48-09 



129-88 

 104-98 



Sc. DiT. 



25-37 



52-46 



117-43 



1-00851 



Sc. Div. 



25-59 



52-91 



118-43 



0-746 



19 5 

 39 28 

 88 21 



,32-0 



From the deflections, Table 6, and the formula 



M 

 X 



we find 



log ^ = 913614 



^X 



= /-3tan«(l + 4 + -iX 



logp^ = 9-88791 



log q^ = 911654 



From the previous equation, 



tan u = 



M 



^^(i+§+S) 



M 

 the values of — , jt?i, and qi, given above, and the values of r from the first column 

 X 



of Table 5, being substituted in this equation, the values of log tan u, column 12, 



have been obtained. 



59. If Y, the vertical component, be substituted for X, in equation (2.), No. 34, 



we shall have, since Y = X tan S 



Y y^X tan/ ^-2+^4;' 



r /•' 



whence 



k = 



tan ti 

 n tan tf 



aY 



where k is the value of -^=- for one micrometer division, u and n are the corrected 



horizontal and vertical deflections for the same distance r ; the former in angular 



MAG. AND MET. OBS., 1845 AND 1846. I 



