Savannah morning news. [volume] (Savannah) 1868-1887, 1881-08-02
one from the other, that a perfect balance

one from the other, that a perfect balance
is brought about, and where this is the case
the telephone makes no sound whatever
The centres of the overlapping coils can
not then be moved either toward or away
from one another without causing the tele-
phone to break its silence. When the coils
are thus balanced and the telephone Is
mute, it is found that what may be called
the area of coincidence, or, in other words,
the area OF overlapping parts Of the two
fats coils, has become highly sensitive to
the approach of metal and manifests its
sensitlveness by a lows note in the tele
phone. AS long as the metal is kept
away from this area the telephone remains
silent but If a piece of lead, for example, is
brought within a distance of four or five
inches from the overlapping parts of the
coils, there may be heard in the telephone
faint but clearly perceptible note, which
becomes louder and louder as the metal
approaches the sensitive surface, and throws
the coils more aud more out of balance. 1t
will readily be seen that under
the guidance OF the telephone a small
area bounded by interesting circumfereuces
Of the overlapping coils can be placed ex-
actly above the bullet or other piece of
metal imbedded in the body, provided the
metal does not lie at too great depth, and
as soon as the balan ced centres begin to feel
the disturbance caused by their approach TO
theimbedded bullet the telephone announces
the fact by faint, continuous musical note,
and this note grows louder and louder until
the overlapping parts of sthe coils are di-
rectly above the disturbiHgmetsl, when the
sound reaches its maximum. For convent
ence of application to the body the coils
used by Professor Bell this morning were
mounted in rec angular piece Of walnut,
about seven inches in length by four in
breadth, with screw posts at the corners for
the wires, and a handle at the back, by
which it could be held.
The following is Professor Bells report to
the surgeons upon to days experiments:
VOLTA LABRATORY, 1921 CONNECTICUT
AVENUE, WASHINGTON, ID. c., August lst,
1S81.-TO the Surgeons jn attendance upon
President Garfield. GENTLEMEN-I beg to
submit for your information brief state
ment of the results obtained with the new
form of induction balance in the expert
ments made this morning for the purpose
of locating the bullet in the person of the
President. The instrument was tested for
sensitiveness several times during the course
of the experiments and found to respond
well to the presentation of the tlattened
bullet at a distance of about four inches
from the coil. When exploring, the coils
were passed over that part Of the abdomen,
where a sonorous spot was observed in the
experiments made on July % feeble tone
was perceived, but the effect was audible
a considerable distance around this
spot, but the sounds were too feeble
to be entirely satisfactory. As l
had reason to expect, from the
extreme sensitiveuess of the instrument, a
much more marked effect, in order to sscer-
tain whether the sounds might not be OBJ
tained in other localities explored the whole
right side and back below the point of en-
trance Of the bullet, but no part gave indi-
81 4Eo, NF al
area of about two inches in diameter, con-
tanning within it the spot previously found
to be sOnorous. The experiments were
repeated by Mr.. fainter, who OBJ
tanned exactly corresponding re-
suits. We are therefore justified
in concluding that the ball is located
within the above area In our preliminary
experiments, we found that a bullet like
the one in question, when 10 its normal
shape, produced no audible effect beyond a
distance of two and half inches, while the
same bullet, hattened and presented with
its face parallel to the plane of the coils,
gave indications up to a distance of nearly
five inches. The same flattened bullet, held
with its face perpendicular to the plane of
the coils, produced no sound beyond a dis
taDce of one inch These facts show that
in the ignorance Of the actual shape and
mode Of presentation of the bullet to the
exploring instrument, the depth at which
the bullet lies beneath the surface cannot
be determined from our experiments. l
am, gentlemen, yours truly
ATrVANnpp p AHA N