6 
M 3 , M Lagat) 
R= (2-3sin’ 9), R=, (2-3sin’ 9); 
e’ and ¢’ denoting the corresponding quantities for the second 
bar. Also, if a denote the distance between the centres of the 
deflecting and suspended magnets, we have 
M 
Substituting these values, and observing that sin® ¢ = sin’ ¢, 
very nearly, 
te as a\ n 
2 -Bsin 9) (7S + Vo) 
n 
‘Now, if 5 denote the horizontal distance of the axis of 
each bar from the centre of the suspended magnet, and h the 
distance of their centres above and below the plane in which 
the latter moves, we have 
2a(ath+B, e2=(a-hP+B; 
accordingly, if we expand a’ e~*, a®e*, according to the as- 
cending powers of : ; 4 (stopping at the second), we find 
ab as me Ai ad h 
(ales agate V ua Noes .. Was 
Vat A (V+ ) (1465 1B)3V V)-3 
in which, since V and /’ are nearly equal, the term 3 (V’-V) : 
may be neglected. Also sin? ¢ = f = a q.p» And, substi- 
tuting these values in the formula obtained above, it becomes 
2747)(14 git 3) 
a~ a~ nr 
But p=(V+V’y cotan 6; wherefore, finally, 
2h? - =) n 
az 
p= 2eotand {143 = 
‘In my original instrument there was but one iron bar ; and 
it was placed in the vertical plane passing through the centre 
of the suspended magnet, and perpendicular to the magnetic 
