38 A. G. Bell—An Induction Balance, ete. 
arrangement. It will also be noticed that the apparatus re- 
quired to be adjusted to complete silence in order to obtain the 
maximum effect 
As a general result of all our experiments with voltaic bat- 
teries, we find that 2 7s advisable to use a battery possessing great 
electro-motive force and slight internal resistance, and to connect the 
cells in series. 
Experiments upon Living Subjects.—On the 22d of July an 
experiment was made at the request of Dr. Bliss upon the per- 
son of Lieut. Simpson, who had carried a bullet in his body for 
many years. 
When the exploring instrument (fig. 11) was passed over 
the lieutenant’s back a sonorous spot was found, but the indi- 
cations were too feeble to be implicitly relied upon. Imagina- 
tion very easily conjures up a feeble sound like that observed, 
but a number of experiments by different observers seemed to 
indicate that in this case there was an external cause for the 
sound—probably the presence of a very deeply-seated bullet. 
The results of this experiment were communicated to Dr. Bliss 
in a letter dated July 23d, 1881. 
On the 25th of July, Prof. Rowland visited me at Washing- 
make any experiment. After our conversation with Prof. 
Rowland, however, we were so impressed by the importance of 
the point that we obtained a condenser next morning, an 
found it to produce not only a different quality of sound when 
the bullet approached the coils, but also to increase the hear- 
ing distance of the instrument shown in fig. 11 at least one 
centimeter. 
n the evening of the same day (July 26th) our apparatus 
was carried to the Executive Mansion, and an experiment made 
upon the person of the President. 
rom some cause then unknown a balance could not be ob- 
tained, and the results were therefore uncertain and indefinite. 
It was discovered afterwards that a mistake had been made in 
the mode of connecting the condenser. The latter should 
have been connected at EF (fig. 13), whereas it was placed at 
KE G, thus influencing only one, instead of both, of the primary 
oils. , 
With the condenser properly arranged experiments were 
_ tried on July 29 and 80 on three soldiers from the Soldiers’ 
Home who had been wounded during the civil war, namely, 
John Teahan, Asa Head, and John McGill 
In the case of John Teahan no results were obtained. In 
the case of Asa Head, who had a buckshot in the cheek, loud 
