Every evening, Wilmington daily commercial., 1919-12-17
PLATINUM FAR At REAR
LOCATED GERMAN GUNS
Professor TroWbridge Tells of Sci
entific Method Of Finding
Big Cannon.

How O little piece Of platinum, electri-
| caIly heated placed on the top Of az empty
kerosene Gun and wired up with other
apparatus, FAR in the rear, located German
guns and helped win the war was ex
planned to the members of the Franklin
| Institute Philade pha, a day or two ago
| by Professor Trowbridge, Of Princeton
| University.
Doctor Troyvhridge had charge of
! corps Of men who did excellent work in the
| American expeditionary force in sound
/ and flash ranging work for artillery firing
I He has been decorated with the d. >. NJ,
I the D. $ D. and awarded the Legion 0f
Honyr by France for his share in direct
ing these men.
In the former days Of warfare artillery
Was not used To such an extent as ~
make this II. nch Of the service necessary /.
/ but with the Increase in size and numb er
| of cannon il was found that means other
+, than actual observation we're needed 70
j locate enemy batteries Professor Trow-
| bridge who holds the chair ot physics at
! Princeton Offered his services 70 The
government, and was placed IN charge
/ OF this new work.
The need for some method Of spotting
enemy batteries was evident soon after
j me DNiDEEAf 1i lie VII Liz ostit4t AA14A
| ii was found that BY observing enemy guns
! from different stations and reporting to a
+, central bureau that the positions could
be quickly plotted.
For instance, If We have three OBJ
| servers watching the enemy lines about
I mile apart and each one sees the fash or
smoke Of the enemy, they can easily with
| inst truments get the angie from north Of
! that object This Is Immediately !eie-
! phoned 10 a central station There,
] there is large plotting board and map
! with the observation posts clearly marked.
! Then BY following the lines Of sight re-
! ported, the intersections 81 the three
lines will pretty CLOSELY mark the 10
cation desired.
This system was found very excellent
/ for good weather but II rain and fog VAS
! absolutely impossible. 1t Was then found
/ possible BY means OF scientific machinery
/ 10 locate the guns by means Of the sound.
/ This took a delicate and complicated bit
/ of machinery The important work was
/ done bv a small bit Of platinum wire
j heated bv electricity ami connected with
other apparatus which would record all
j changes IN temperature.
This change Of temperature would
/ take place when the vibrations, caused by
] the NOISE OF the shell as it broke the air IN
! passage, and the sound OF the gun. forced
i fresh air against the bit OF wire. SIX such
instruments would be set up along an arc
equidistant from the suspected area
In addition, there would be obSerya-
| ton posts with watchers constantly on
! duty. The posts and instruments were
! all connected to a central station. When
the watchers heard gun fired they
touched button that sent the current
through the delicate wire and started
the recording machinery in motion.
Then by means OF relays 9nd other electri-
cal apparatus We would have the sound
wave photographed on strip OF moving
picture film From thls it "as not DIFF
flcult to deduce By mat hem4tlcs the posi-
ton desired.
This IL lie instrument not only told
Us, by means of the vibration recorded
the location and kind OF gun firing but
also the target being fired at 1t WAS
found that the difference of time between
the sound of the gun aud the sound of the
shell brea king the al gave a great deal Of
this information This latter sound must
not be confused With the whistle or
shrek OF the shell which is caused by the
wake of air following he projectlle
The accuracy with which the work was
done is remarkable During the 81 Mi
hiel drive. III a period of three weeks of
advance, the corps found 425 separate 10
cations of enemy batteries OF these two
American fash posts found IS per cen
and three French posts got q per cent
Three American sound posts located q
per cent
\ little later during a stationary peri
oil in which 1872 positions were located
three American flash posts found 3S per
cent, two French flash posts 3 per cent and
three American found 81 per cent. The
American we're much faster and worked
with far greater accuracy than the French.
II took but six or seven observations to 10
cate within twenty yards Of an enemy
battery
''The Germans tried ear sound ranging
but il was inefficient and slow We did in
two minutes what il took them about
three-quarters of an hour.
In closing Doctor Irow bridge paid
tribute To the men wh worked under him.
''lt Is entirely cue To them, he said,
that the work Wa successful | was but
the tigurehead and director The honors
which | have since received are but
tribute to them given me because | hap
pened to betheir leader They worked
tirelessly, without rest or leave, aud only
about 1000 of them served the entire
army. Phi ade phla I.edger
-e