Daily press. [volume] (Newport News, Va.) 1896-current, 1898-07-17
FINDING THE RANGE.
HOW BIG COAST DEFENSE GUNS ARE
ACCURATELY AIMED.

ACCURATELY AIMED.
The Many NIathematical Problems 1nvo,,
ed aud the Great Rapidly with whic
ahey Must Be Solved In Locstsng tn
Moving Target.
a reporter for the Boston Herald give
inns interesting account OF q talk with on
~. " ehe regular army officers at Fort Ha,n
nton, In Boston harbor: :
III the days of the civil war rance
We SO very short that the gunner had n
uilnculty IN seeing his target and lawn.
Us Us suh oirectly upon 1t. Wind and spcet
VI Target cut no figure because the n,,oiect
lie had such short distance to nass 80
tnat neither had enough time to act t.
mike any apprecinble difference. Bu
Low "hcn firing at U target eight mile.
away all of these things make thcnselvcs
1elG. There is the rifiing in tho born
"hlch gives the projectilc the rotation
necessary TO Keep it from tumbling and
wy, VII III our service carry the pro,
1eoaAle 70 tho right Then the direction
anu force OF the wind, the direction and
speed or target, the temperature and h,r.
othcurlc pressure of the air which affect
s'ie resistance OF the air to passage of tho
y proJecSilc, tho kind of powder anu weight
Ct proJect1!e. All these things have 1o he
Saken into account and they each vary
sanoer al sorts of conditions, SO that thew
o,s Wy pe figured ouefor each particular
snoG,at the time the gun is fired.
Most Of this information must ha
Worked out from data obtained from fir
ing tests and must be thoroughly assin,i-
!aleo by the expert artillcrist. Then IN,
enh1hg observations ut the time of firiur
uata are obtained from which r,s,,lts c.,,,
= be computed '
ne most important pdTt of the opera
son rs OF course to locate the target. The
invention which has enabled us 10 do this
As something wholly Americana dev,.lon
inent of our regular army This Invention
IS emo range finder. 1t looks Il si.nn]e af
Aaif-a tail modern tower, with "A sinh
stahtlal foundation, built on "a command
ing height and connected with the runs
perhaps half a mile distant, by telephone
al INC top is u large telescope, adjusted on
poilshea steel circular table. A dial on
the telescope frame is cor..cl win ~.
edge of the circular table ana ,,ivn. ,t ~.
Instant the direct rcatiiu., in ,zin,,,.,
another dial is so arranged that elcy,,i,n |
OF depression OF the telcscone uiy.s ire |
shuicator Il corresponding movement. This |
IS ike the ordlnary transit fitted to reuti |
vertical angles, but in this ease insto,a
oi reading angles of depression distances
.iro inuicatcd III yards to the point where
1n . INC OF sight pierccs the water An
.adJust1nent corrects for height Of ride
IS only Necessary, then. TO noint o,,r
5selescoGe at tho water line Of the shin
s1nsl resauS lrectly ayimuth and distances
s.Ee ira Tss,l, lifted by telephone
80 ealss s. Jhese obsery
20 seconds apart, nro plotted, and the gLs>
has to be fired so seconds after the last
observation is taken OF at the end OF two
minutes total time We have the location
OF the target ut three different ti'acs. 1t
is now necessary to compute where it will
be at the end of the so seconds. -
GA vessel running IL knots IN hour
will pass over 200 feet in one minute or
1900 feet in so seconds, SO that If we fired
at the point whore she was at the last OBJ
servution we might miss her l, 500 feet or
some fraction OF that. depending on her
direction of sailing with reference to us.
If we fired point blank G., aiming right
at her we would miss as much as she
would pass over in the time of flight Of
the prcjcctilo. This for q 10000 yard !
range might be 90 seconds.
tive have now the position of the target
ut a given future instant, but it is referred
to the position of the range tower. Wo
must now correct our data to refer to the
guns position. Then we nre ready to
make corrections for drift duo to rifling,
effect of wind, condition OF atmosphere
and abnormal powder and proiccuils. Tho
gun is laid with the resulting data by
means OF degrees and minutes marked on
the traverse circle Of the gun platform and
elevation arc on tho side of the carriage,
and wc are ready to fire. 1t is necessary to
allow timc-callcd time of fight'-for
the projectilc to reach the target at the
end of the so seconds, so the guns must be
fired that long ahead of time
'sWhen you consider that all OF this work
must DO done in SO seconds, you see that
ono has to count his time by fractions of
seconds to work like an autolnaton. No
longer time can be allowed for conputa-
tions, ETC., es uncertainties Increase as
about tho fifth power OF the timo.
'sThc aiming of tho gun is all science
now and needs experts. The firing and
loading arc tho Only work which tho un-
trained mind can find work Mt, and even
In these things you understand, there is
need Of GOODNESS and experience for these
big fellows are delicate machines, after
f all, and arc worked BY levers, have elcc-
trical appliances ard are in other ways too
precious to trust to untrained hands.
szS'sThis may not sound SO dreadful hore
I in the calm Of q peaceful afternoon. But
imagine looking up sincs and cosines
plotting accurate curves from mathemat-
rs ical data under q hail OF projectilc, with
5ss shells and bombs bursting around you
sa Fancy placidly sighting your telescope in
1.-THE range tower, which u we'll directed
22s shot may cut away from beneath you, and
your hand must not tre1nble, your mind
must not be distractedI"
The civilian seemed rather impressed.
He could only venture timidly that it did
seem as if there were great odds against
the ships
$50 there are Bnt they have advan-
3 tages too. In the Japanese Chinese wan
"A the Japs, being clever got ahead of the
Chinese predictions of their position by
Z running ahead full speed and then sudden
II ~ Stacking up, so that the Chinese gun
n ners began to grasp that ruse. Then they
changed their tactics and would advance
H slowly at first, then suddenly crowd on al
steam and speed away, leaving the gun
E ners far behind"