32 A. G. Bell—An Induction Balance 
the best shape of coil. 
structed the instruments shown in 
For this 
purpose M 
fig. 8 
r. Tainter con- 
ircular grooves 
were turned in two boards, one of which is shown in perspective 
at A and the other in section at D. An insulated copper wire 
Oo as to 
ive the 
king an experiment with this apparatus the secondary 
n ma 
coil (B) was first placed within the primary ring and 
produce silence. ° : 
horizontal rod until the balance was sensibly disturbed and the 
relative distances of the coils and the brass ring were noted. 
The brass ring C was then mov 
in the 
RESULTS OF A SERIES OF EXPERIMENTS MADE ON THE 19TH OF JULY, 1881. 
Distance between— 
Distance between— 
Pines F of | | mene Aha aes es 
LS | Oe | esueeeres AB | BO’) AC 
| a | 
mm. mm. mm mm. | mm. / mm. mm. mm. 
er ae ae ee ee ee 
Gos [ee 19 | 5 20 25 
30 10 --f 48 23 159 | 10 18 28 
90 9 29 F390 17 37 
360 °°4 7 31 30 14 44 
50 0 50 50 14 64 
Oc at 17 0 12 12 
pF. ae 24 5 18 23 
a0 10 } 26 36 206 10 25 35 
| 20 17 37 20 19 39 
| 30 14 44 30 22 52 
50 5 55 50 18 68 
Oot 2) 21 0 20 20 
bo OF 28 28 5 18 23 
81 ee Ca vee 3 33 253 10 20 30 
fae 5 18 38 20 19 39 
| 30 14 44 30 23 53 
| 50 12 62 50 20 70 
0 22 22 
ae 25 30 
113 164 27 37 
| 80 4. 96 46 . 
| 30 | 36 56 
bs OO 67 
