30 A. G. Bell—An Induction Balanee, ete. 
that which had struck the President. Even when such a bullet 
was flattened by being fired against a board, and was presented 
with: its flat side toward the coils of the explorer—-the most 
favorable mode of presentation—no better result was obtained. | 
Original Experiments.—In the theoretical arrangement recom- 
mended by Professors Trowbridge and Rowland (fig. 6) the 
primary coil A was of smaller diameter than the secondary B. 
This had given us no better effects than the ordinary form of 
Hughes’ balance (see fig. 2), in which the two coils A B were 
of equal diameter. We then tried the effect of making the 
primary coil A of greater diameter than the secondary B (see 
fig. 7), and in this case we appeared to obtain an increase of 
at: 
Bi: 
WU 
AY 
oe 
x 
re 
‘3 
< 
hearing distance. Five centimeters (2 inches) was, however, 
the utmost limit reached, when, on the 19th of July, Mr. J. 
Stanley Brown and Dr. Woodward visited my labcratory and 
witnessed some experiments. No difficulty was experienced in 
detecting a bullet held in the mouth by passing the exploring 
coil over the cheek; and the presence of a flattened bullet held 
in the clenched hand wasalso readily determined. Dr. Bliss, Dr. 
Reyburn and Surgeon-General Barnes visited the laboratory 
next day and expressed themselves as very hopefully impressed 
by the experiments. These were subsequently repeated in the 
surgeon’s room at the Executive Mansion, for the information 
of Dr. Frank Hamilton and Dr. Agnew, who also seemed favor- 
ably impresse 
uch opinions from the surgeons in attendance upon the 
President, and the continued interest shown by Professor New- 
comb, encouraged me to proceed with the experiments.* 
It was now determined to test the effect of each convolution 
of the primary coil, so as to arrive empirically at some idea of 
*T desire specially to express my gratitude to Dr. Frank Hamilton for words of 
encouragement spoken at a later date when sympathy and encouragement were 
greatly needed. 
