The daily dispatch. [volume] (Richmond [Va.]) 1850-1884, 1881-08-02

which the current Is 10 be induced. are car
ried to the binding parts OF the Bell tele'
phone. When the connections have all thus
been made the secondary coil ID laid on the
primary or inducing coil so thai their re-
specliye circumference exactly coincide.
lThe circuit. breaker Is then set In mo-
| ton, and the rapidly Interrupted cur
rent through the primary coil induces
another current OF higher intensity 10
the secondary coil, and as IL does so
loud musical tone Is heard IN the telephone
with which the secondary coil Is connected.
As long as The current is maintained and the
circumference Of the two coils are kept IN
exact condolences the musical note In the
TELEPHONE does not change It's pitch or IN
tensity. IL, however, the experimeDter
slides up her coil along an inch or so upon
the lower coil, 50 that their circumference
no longer correspond, the intensity Of
the musical tone Is diminished; aud
lust IN proportion as the centres
at the fiat coils are separated by
greater or less distance the Intensity OF
the musical tone Is lessened or increased.
When the upper coli has been Sudden over
the lower so that they simply overlap the
centre Of the one corresponding nearly with
the point on the circumference OF the other
The upper coil be pushed little farther 10
one side, so that IL overaps, a still less tone
is again heard. By delicate manspulation
II is possible to adjust the centres OF the
overlapping coils OF such distance one
from the other that perfect balance is
brought about, and when this Is
the case tbe telephone makes no
sound whatever. The centres OF the
overlapping coils cannot then be moved
either toward or away from one another
without causing the telephone TO break It's
silence. When coils are thus balanced and
the telephone i mute il is found that what
may be called The area OF coincidence, or III
other words the area OF the overlapping
parts Of the two lat coils has become highly
sensitive 10 the approach OF metal ana mani
tests its sensiliveuess by low note In the
telephone. As long as the metal IS kept away
from the area the telephone remains silent,
but il piece OF lead, for instance, is brought
within the distance Of four or five inches
| from the overlapping parts OF the coils,
there may be beard IN the telephone iaint
but clearly perceptlble note, which becomes
Iouder and louder as the metal approaches
the sensitive surface and throws the coils
more and more out Of balance. II viii
readily be seen that under the guidlnce Of
the telephone the small area bounded by The
Iintersectine circumference OF overlapping
coils can be placed exactly above q
bullet or other piece OF metal imbedded
in a body, provided the metal does not lie
at too great depth. As soon as The bal
anced coils begin to feel the disturbance
caused by their approach to the lmOedded
bullet the telephone announces The facs by
faint, continuous musical note, ana thls
10
note grows louder and louder until the
overlapping parts OF the coils are directly
above the disturbing metal, when the sound
reaches its maximum. For the convenience
Of application 10 the body the coils used by
Professor Bell this morning were mounted
in rectangular piece OF walnut about seven
Inches i'm length by four in breadth, with
screw posts at the corners foI the WlIts ana
a handle at the back by which it could be
held The following is Professor Bells re-
port to the surgeons upon TO days expert
mentS
Vata LaJrdtory 1921 Connecticut due
n,e. WnShtnqtOn, d. C., August |. $751;
To the Surgeons in attendance upon Presi-
dent Garfield: GenlIcmen,-l beg TO sub
INIT for YOUR information a brief statement
lof the results Obtained with the new form OF
induction balance in the experiments made
this morning for the purpose OF locating
the bullet in the person OF the President
The instrument was tested for senstlycncSs
several times during the course Of the cX'
ntriments, and It was found TO respond wei
10 the presentation Of the 1lttened bullet al
the distance Of about four inches from the
lcoils. Wien exploring the coils were
pasSed over that part Of the abdomen where
"A sonorOus spot was observed, IN the eX
Deriments made on July 26th, feeble tone
was perceived, but the effect was audible
considerable distance around this spot
The sounds were too feeble TO DC
entirely satisfactory, as | had reason
10 expect, from the extreme sensltlYenes'
OF the instrument, Il much more marked
effect. In order to ascertain whether SINH
lar sounds might not be obtained In othel
localities | explored the whole right side
and back below the point OF entrance OF The
bullet, but no part gave indications OF the
presence Of metal except an area Oh aDou
Two inches in diameter, containing within
it the spot previously found to be sonorous
The experiments we're repeated by Mr.
Tainter, who obtained exactly correspond
ing results. We are, therefore, justified II
concluding that the ball Is located
within the abOye-named area. In on
preliminary experiments we FOUND tna
the bullet, like the one in question, when II
its normal shape produced no audible ehec
beyond the distance OF two and half Inches
while the same bullet n1ttened and pre-
sented with its face parallel to the plane o
coils gave indications up TO the distance 0
nearly five inches. The same flttcned bul
let, held with It's face perpendicular TO tn
plane Of coils, produced no sound beyond
distance OF one inch. These facts show tina
i'm ignorance OF the actual shape and mod
OF presentation OF the bullet to the exploring
instrument the depth at which the bulle
lies beneath the surface cannot be deter
mined from our experiments.
| fam oentlpmpn VOUrs truly.