YERDET’S CONSTANT IN ABSOLUTE UNITS. 
7 
The observations being repeated at each of the seven points, we have the intensity of 
the magnetic action of the helix at each of those points in terms of that of the dyna- 
mometer. 
Thus if P be the power of the dynamometer with unit current, and u x the power of 
the helix with the same current at a point x, then the total force of the helix (that is, 
the difference of magnetic potentials at its ends) is 
C 6 ' 1 j -p (H + R 0 . H + E 
N J. %^=io p |d+?;+d+^ 
H + E 2 7 j . H + R 47l 
' + 
D + r< 
+ 
H + R(j/, 
D + r 6 /t 
+5 
/ H + R, 
\V+r, t 
H + R,A i /» H + R 3/ A 
where h is ^ the length of the helix. 
In the helix used the following results were obtained : — 
7i=4-39 centims., 
p R + H H= 1-01, take = LOO, 
1 r + D’ D = 28*15 „ 28*1. 
r= 100. 
r = 200. 
r=1000. 
M 0 
p 348 + H_ 7 4 p 
100 + D 
p 629 + H_ 2 _g Q p 
200 + D 
p 2797+ H — 2’722 P 
1000 + D 
u \ 
p 636 + H = 7 p 
100 + D 
p "« 3 0 4 +d 4 ' 976 P 
P 5iM±H =4 . 9 62 P 
1000 + D 
u 2 
p tw 5= 6 - 667 P 
p m ! = 5 - 65S ' p 
p 5840 + H =5 . 681 p 
1000 + D 
«8 
p 1£H- 777 P 
p 1315 + H_ 5<725 p 
200 + D 
p 5960 + H_ „ p 
F 1000 + D- 5 798 1 
m 4 
p 713 + H_ 5<3 ^ 4 p 
100 + D 
p 1270+ H_ 7 p 
200+0 
p 5750 + H_ p 
1000 + D 
u b 
p 615 + H =4 . 808 p 
100 + D 
p 1097 + H_ 4 . 814 p 
200 + D 
p 4969 + H =4 . 6 
1000+D 
U B 
p 348 + H_ 2t724 p 
100 + D 
p 620 + H_ o ^ g p 
200 + D 
I p 2799 + H 2*723 P 
| 1000 + D ' 
Hence we have for the values of u n by taking the means of the above, — 
-■ 
u 0 . 
u x . 
■S- 
U i m 
*■ 
* 
r— 100 
2*724 P 
4*973 P 
5*667 P 
5*777 P 
5*574 P 
4*808 P 
2*724 P 
r— 200 
2-762 P 
4*976 P 
5*659 P 
5*725 P 
5*572 P 
4*814 P 
2*722 P 
/*= 1000 
2*722 P 
4*962 P 
5*681 P 
5*798 P 
5*592 P 
4*639 P 
2*723 P 
Mean ... 
to 
■^1 
03 
* 
4*970 P 
5*669 P 
5*766 P 
5*579 P 
4*754 P 
2*723 P 
