40 
NATURE 
[ Voz. 10, 1881 
subsequent annual charge at about 2000/7. It would 
seem therefore that we may shortly expect to find a 
tolerably complete and well-equipped observatory in the 
most eastern of our possessions. It is believed also that, 
with the assistance of Mr. Hart, the Inspector-General 
of Chinese Customs, the Government of China may be 
induced to establish a series of meteorological stations at 
various points on the seaboard of their vast territory. A 
perusal of Major Palmer’s report leaves on our mind the 
impression that the Colonial Government is fortunate in 
being able to obtain at the present time the advice and 
co-operation of an officer of his ability and scientific 
attainments. 
PROBING BY ELECTRICITY? 
pee instrument? I have the honour of presenting to 
the Academy has for its object the determination of 
the exact place occupied by balls of lead, fragments of 
shell, or metallic substances of any kind embedded in the 
body of a person wounded by firearms; and it may be 
considered as a form of the well-known induction-balance 
of Prof. Hughes. 
This exploring instrument enables us to determine that 
position fur the most part with very great exactness, and 
that without any pain to the patient, which is not the 
case when we use metallic probes, which require to be 
brought into direct contact with the projectile. 
The instrument is composed essentially of a system of 
two parallel flat coils partially superposed upon one 
another in such a manner that the edge of one is nearly 
over the axis of the other (Fig, 1). One of these coils 
i ee ee 
(a) is made of thick wire constituting a portion of the 
primary circuit, and the other (B) of thin wire, consti- 
tuting a portion of the secondary circuit. Both coils are 
imbedded in a mass of paraffine placed in the interior of 
the wooden case furnished with a handle. 
A vibratory current from a galvanic battery traverses 
the primary coil, and the secondary circuit includes an 
ordinary telephone. Under these circumstances no 
sound is heard from the telephone ; but if we cause any 
metallic body to approach the part (C) common to the 
two coils, the silence immediately gives place to a sound 
the intensity of which will depend upon the nature of the 
metallic body, upon its form, and upon its distance. We 
may remark in this connection that the most favourable 
form that can be assumed by the projectile for which we 
explore, is that of a flat disk with its face parallel to the 
surface of the skin, and that the most unfavourable, a 
similar disk with its face perpendicular to the same 
surface. 
It is difficult in practice to obtain the exact adjustment 
of the coils required, and it is therefore found advisable 
to introduce into the primary and secondary circuits 
1 Upon an Apparatus for Determining without Pain to the Patient the 
Position of a Projectile of Lead or other Metal in the Human Body. Note 
by Prof. Alexander Graham Hell, read by M. Antoine Breguet at the Paris | 
Academy of Sciences. Contributed by the Author. 
2 This instrument has originated from researches undertaken in the Volta 
Laboratory at Washington on the occasion of the sad attempt upon the life 
of President Garfield. ‘Ihis Note is preliminary to a paper which I shall 
publish shortly, giving a complete account of these researches. So many 
different persons have been kind enough to give me the benefit of their 
suggestions and advice concerning the method of exploration for this object, 
that I can only mention here the names of a few: Prof. Hughes, George M. 
Hopkins, Sumner Tainter, Thomas Gleeson, Dr Chichester A. Bell, Charles 
E. Buell, Prof. Simon Newcomb, Prof H. A. Rowland, M_ Rogers, Prof. 
John Trowbridge, J. H. C. Watts, the director of the Western Union 
Telegrapn Company at Washington, and the correspondent of the WVew 
York Tribune at Washington. 
respectively two other coils (D and k, Fig. 2) analogous 
to the first, but very much smaller, whose common sur- 
face can be modified by the play of a micrometer screw. 
By means of this fine adjustment we are able easily to 
reduce the telephone to the most complete silence, It 
should be added that the effects obtained when a con- 
denser (F) is introduced into the primary circuit are 
much inferior to those obtained without, as had been 
independently predicted by Prof. Rowland of Johns 
Hopkins University. 
If we wish to ascertain the depth at which the metallic 
mass lies embedded this is easily ascertained if we know 
a priori its form, its mode of presentation, and its sub- 
stance. It is only necessary to adjust the apparatus to 
Ce 
\ 
Geos; 
jf 
Fic. 2. 
silence while it is applied to the skin, after which, re- 
moving the apparatus, we bring near it another metallic 
mass similar to that explored for, so as to reproduce 
silence anew, and the distance of this mass from the ex- 
ploring instrument gives the measure which it is desired 
to determine. 
I conclude this Note by the relation of an experiment 
made in the office of Dr. Frank Hamilton of New York, 
on October 7 last, in the presence of thirteen eminent 
surgeons.! The experiment was made upon the person 
of Col. B. F. Clayton, wounded in 1862. The ball 
entered in front through the left clavicular articulation, 
breaking the clavicle. Doctors Swineborne and Vander- 
pool supposed that it was lodged under the scapula, but 
my apparatus demonstrated, on the contrary, that it was 
located in front and just below the third rib. 
MAGNETIC SURVEY OF MISSOURI 
jf NATURE, vol. xxiii. p. 583, the writer presented a 
chart of magnetic declination which represented 
the results at forty-five stations in Missouri. The facts 
seemed to indicate a marked effect due to contour. Up 
to the middle of August of the past summer nothing 
inconsistent with this explanation was found, although 
the number of stations had been increased to over eighty. 
By that time the stations had become so numerous in 
Central Missouri that a more minute survey along the 
river bank between Jefferson City and Glasgow gave 
promise of affording a crucial test. It was necessary that 
the 8° line, which bends down the river, crossing at some 
point east of the mouth of the Osage River, should 
vetuyn on the south side of the river, looking something 
like a reversed contour line. 
What we did find was, that the 8° line crosses the 
Missouri Valley wzthout bending, running south-west to 
near the summit of the “divide” between the Osage and 
Missouri rivers, and ¢iez bends abruptly to the north- 
east, re-crossing the Missouri above Jefferson City, and 
1 Doctors G. H. Gardner, G. Durant, Ed. Birmiogham, N. Bozeman, L, 
Damainville, J. N. Hinton, Francis Delagield, F. H. Hamilton, D. Cham- 
berlain, Elias Marsh, J. G. Johnson, Joseph Halderson, and J. G. Allan. 
