Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1898-08-27
BUFFALO LlTHlA WATER

diately.
VERTICAL BASE LINES PREFERRED
When a horizontal base line is used II
Is necessary 10 have an instrument az
each end of it. But style of range
finder has recently come into vogue which
makes the use Of vertical base line and
needs only one instrument This is
set up at distance of fifty or hundred
feet above sea level, and it's exact eleva-
ton is ascertained with scrupulous care.
Now, the angle which this vertical forms
with line run from its lower extremity
to the ship whose distance is about 10 be
measured is. of course, right angle
under all circumstances. It is necessary,
therefore, to get only the angle at the
upper end Of the vertical This fact sim
pllfies matters greatly. Down at Fort
Monroe, where a horizontal base line Is
used-one that is over mile long, by the
way-a telephone is required at each end.
However, there is a curious tele-
graphic attachment that reports at one
end of the base. which is inside the fort,
the readings at the other end, and thus
permits all the calculations to be made
in one spot.
At Fort Monroe It has been found that
a target fifteen feet square can be hit
every time at a distance OK 1900 feet.
The guns are provided with graduated
scales that tell the gunner how much
TO elevate his piece for any particular
distance Hence, when the man at the
range-fnder once gives him that factor
in his problem, all the rest Is compare
lively easy work.
One might think that where the base
line was over mile long 1t would be
ha wit a
much shorter one. But this story IS told
regarding the first work done at one of
the forts near this city with the instru-
ment which uses a vertical base line.
The officer OF a gun squad was about TO
indulge in little practice. He had
figured out the distance Of his target the
night before by means of a horizontal
base line as 1900 yards, or 1900 feet
which Is fully five miles. Another man
stationed at a new range-fnder which
used a vertical base was on duty at the
same time. He remarked 70 the officer
that he estimated the distance at $500
yards The officer was sceptical, because
he had already computed the range in
the old way. And he began his practice
on that basis
The great 10-inch rifle was aimed and
fred. Out near the target was an obser-
walton tower, from which a telephone
message reported: Five hundred yards
short; so many to the left" The officer
ROW consulted the man at the new range
finder and acted on the latter's advice.
six yards over and two TO the left,
was the next announcement from the
observation tower. One more correction
for lateral deviation was made, and then
shot after shot hit the target without
T.. In oh
works at the upper end Of a vertical base
line is called a depFession-fnder, pro-
badly because it must be inclinr3 down
ward very slightly from a hor..4'..N. 10
cover the distant object At .-.iv rate,
1t is a wonderfully accurate and compa-
ratvely simple instrument.
FIRING AT A MOVING TARGET.
It is one thing, however. 20 bang away
at a big float that is anchored out in a
bay and another to hit a ship which is
moving rapidly, even though It be coming
almost straight for the port which IS
trying to repel its attack During the
short period OF time required for ascer-
tanning the ships distance and cOmmuni-
eating the proper instructions GO gum
ner. a change of aim has become neces-
sary. II is customary. therefore, for
the operator at the range-hnder TO cone
pute the probable position OF a ship two
minutes hence, and TO instruct the gum
ner 10 set his piece accordingly.
A cannon is mounted with two sets Of
graduated circles, one measuring angles
OF motion sideways, and the other motion
I'D and down. In aiming a gun, of
course. II is necessary to move It In both
WAYS Now the man at the range-inder
telegraphs 10 the gunner TO set his gun
bv these graduations, and gives him the
right readings for that purpose. The
gunner IS thus relieved Of a part of his
responsibility. When the ship reaches
the position which the operator had
contemplated, he either discharges the
gun GEOGRAPHICALLY himself. or flashes up
in front Of the gunner signal to fire.
on shlpboard the horizontal base line
&c employed. This is from two hundred
10 three hundred feet long. one end being
IN the bow and the other well aft BY
providing one INSTRUMENT with automatic
annaratus. like that at Fort Monroe, for
renorting the angle to the other station,
II Is possible 10 get along with single
operator. But difficulties are experienced
AT sea that are not encountered on land.
The roll OF the vessel complexities the
task OF observation and OF training guns.
And in an engagement like that between
Schley and Cervera, not only is the enemy
changing his position. but the assailant
ts doing so, too. Nor Is II always straight
running like that on race-track.
Sometimes a vessel VIII present her
broadside to the foe in order 10 deliver
an effective fire, and then will turn so
as 10 ram. This kind OF manoeuvring
makes the task OF the operator ar the
good deal harder than say
Inc hfs 4 b. Cs.