26 A. G. Bell—An Induction Balance 
idea of using a magnetic needle to indicate by retardation of 
its rotation the proximity of the bullet in the body of the 
President, and I telegraphed to Prof. Newcomb the offer of my 
assistance in carrying on experiments, knowing the compara- 
tive diffic my he would experience in having apparatus made 
in Washingt 
At his Saanec I tested the point whether the rotation of 
a leaden disk and of a‘ leaden bullet underneath a delicately 
‘suspended magnetic needle would cause a deflection of the 
needle. 
The disk occasioned a deflection, but the builet produced no 
mene effect. I telegraphed the result to Prof. Newcomb, 
at the same time took occasion to inform him of the hope- 
fal results I had obtained with the crudely constructed induc- 
tion balance referred to above. 
I was much gratified by his immediate appreciation of the 
experiment. He telegraphed that he thought an induction 
balance promised a much more hopeful solution of the problem 
than his own oN and encouraged me in every way to con- 
tinue my exper 
This a scacine " detepinared me to proceed to my labora- 
tory at Washington, where I was accompanied by Mr. Sumner 
ba et who was anxious “A assist in such a cause. [ eae 
ceived from Mr. Hopkins, and also a Hughes’ induction bal: 
‘ance like that shown in fig. 2, which Mr. Hopkins bad for- 
warded to the Executive Mansion for trial. 
his apparatus was at once tested in my pie a with re- 
sults slightly better than those I had obtained in B 
My Boston —_ did not give a greater pee a dis- 
tance than 3 cm., whereas with the Pea apparatus I could 
— effects at a distance of 3.75 ¢ 
r. ae og (A B, fig. 2) were then fastened 
upon a peades han o form an ‘exploring instrument, and 
the whole apparatus was Sentaed for immediate use in case of 
pal 7 arising for an experiment upon the — 
I set myself in communication with Mr. Hopkins, and r 
Paierl his assistance and coéperation, and in reply saciea 
through Private Secretary Brown the following account of 
further experiments : 
