The record-union., 1898-06-08
SHARPSHOOTING AT SEA.
How Accuracy Is Secured by Use Of
the Range Finder.

The accuracy of modern rified guns
Is one of the wonders of engineering
Two experimental shots fired few
years ago at the same elevation from
the same gun fell within thirty yards of
each other, after traversing a distance
OF twelve miles. If a modern rifle is
laid upon the target, with proper ele-
walton and allowance for windage, it
is safe to say the shot will find the
mark. The correct elevation of the gun
can only be determined if the distance
OF the target is known, and the exact
determination of the distance of NOV
ing object is a problem that has wor-
ried the gunner ever since the day when
round shot was first thrown from the
sides of the wooden fighting ship.
In the early days the determination
of the range was a matter of guess
work. The gunner assumed a distance,
elevated his gun accordingly and
watched the course of the shot If it
fell short he increased the elevation.
and if it passed over he decreased it.
This was all very we'll in a day when
the guns We're too feeble to do much
execution except at close range, and a
few dozen shot thrown away made lit
tie impression upon a ships magazines.
With the advent of modern ordnance
however, with the siXtytOn guns and
costly charges, the necessity of accu-
rate fire became imperative, and ord
nance experts set about deviSing some
scientific method of finding the range
at sea. The earliest and best known
device of the kind was the invention Of
Lieutenant Fiske of the United States
navy, which has been installed on many
of our ships, and is widely in use in the
various navies of the world.
The Fiske range finder is based upon
the we'll known principles of land sur
veying with the transit and engineers
chain. If a surveying party come to a
broad river whose width has to be de-
termined, base line is measured along
the bank, and the angles which this
line makes with a mark on the OppO-
site bank are measured by the transit.
Then knowing the length of the base
line and the two angles, the distance
across the river can be determined by
trigOnOmetry.
Applying this to the range finder. a
base line is carefully measured between
two points near opposite ends of the
ship and over each point range find
er, answering to the engineers transit,
is permanently set up. If the tele-
scopes Of the two finders are simultan-
eously converged upon the same point
on a distant object (ship. fortress or
city) the observers will be in posses
sion of the trigonOmetrical data neces-
sary to compute the distance, namely.
the base and the two base angles.
In the din, hurry and slaughter OF a
sea fight, however, it would be difficult
to make the necessary calculations, as
the distance between the ships, and,
therefore, the observed angles, keep
changing. and in order to make the
determination of the distance auto
matte, Lieutenant Fiske placed his tele-
scope in the circuit OF a Wheatstone
bridge and caused their change of DO
sition to record the distance of the OBJ
ject on the graduated scale of deli
cate galyanometer. All that was now
necessary was for the observers at the
two range finders to keep the cross
hairs of the telescope upon the same
point of the ship, and the electric cur
rent translated, as it were, the angles
into distances and recorded them by
the movements of needle over an arc
graduated into hundreds and thousands
of yards One of these galvanometers
is placed in the coming tower and one
at each of the principal gun stations
Scientific American.