New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1898-08-14
:ur MODERN RANGE-FINDER.
Az rNEMY's DISTANCE is ASCER-
~ TANNED.
.,,.ruoD IS SIMPLE. BUT THE OPERATOR
MUST BIZ sKILLED-AN ELEMENTARY
LESSON IN GEOMETRY.

Uf
u" ',st few years in the art of warfare is to
'D ..und in the precision with which long
Guns are fired. Not only are cannon
IN that will throw a prOjectile further than
Ds, but devices have been invented which
'' wi. the gunner to hit his target oday as
,a;n,v at a distance of four miles as at one
nrs a generation ago.
~ 49,. ri0eman whether he Is a soldier or
.:.rov a hunter. knows that il he is only
-, roarksman all he needs to know Is the
,.,ance Of the object he wishes to hit. Unless
y. oon determine this, by guess or other means.
=. 10 likely to aim too high or too low. Against
.,n,ol deviation from a straight line he can pro-
r,ac or should be able to. He knows what sort
:, mind is prevailing and can make the proper
.uowonc. But the curvature OF the path taken
=. hs bullet. which is due to gravty-that Is
a. say the drOI,--varies according to the dis
-. and all calculations for this must begin
"a, on estimate OF the number Of yards be
.-.ur himself and the target. The distance
49,, ,sccrtained. he knows just how much to
elevate his rifle.
p~oc;sev the same thing Is necessary with
Ct, Gums whether they are mounted in fort
,',,r,ed 70 defend harbor from an enemys
6nat
.,,,ad "rangc-fndcrs" are intended to ascertain
.,v Tar away the foe is. Several devices OF
,h,s class have come into use in the last few
years. but they all work on the same general
s.,,o;r,s II is one of which surveyors are con-
,nually making use. and the astronomers also
.nnov it to ascertain the distances OF the stars
This underlying principle Is very simple one
The student Of geometry learns carly in his
.ourse OF study that II the length OF one side or
,,riange and the angles which this side forms
Nth the other two are once known 1t Is easy TO
er,re out the length of those two sides also. The
snrveyor. the astronomer and the man who uses
. range-fnder start with one side or triangle
which they call their base line. and imaginary
us.e drawn from the two ends of II 10 the dis
,.rt object are the ones whose length is to be
ascertained
The base line. which in many cases is hori-
eontai Is very carefully measured to begin WILL
A small telescope. with proper attachments for
ascertaining angles is now stationed al each
end OF this line and trained on the OBJECT WHOSE
distance one wants to learn. Some range-hho-
ora ar. so made that when these angles nave
been measured a good deal of figuring must De
aone N get the desired result. Others tell the
distance Immediately.
VERTICAL. BASE LINES PREFERRED.
When a horizontal base line is used it is neces-
sary TO have an instrument at each emu Oh It.
But a style Of range finder has recently 'o''e
,,,o vogue which makes use Of a vertical base
line and needs only one instrument Inns 70
ss nm at a distance OF fifty CT hundreu iee'
above sea level. and its exact elevation Is aSoe
famed with scrupulous care NO" inc a"s'
,~,ioh THE vertical forms with line run from
u. ,ouer extremity TO the ship whose distance
q. ohou, IN he measured is, Of course. right
angle under all circumstances. 1t Is necessary >
therefore TO get only the angle at thr upper
end NJ the vertical This fact simpliiies matters
greatly. Down at Fort Monroe where Il horizon
tai base line is used-onC that Is over mile ioi 8.
nv tbc v,av-a telephone is required AT each end
However there is a curious tclegraphic a''ach-
nent that reports at one end OF the base Which
IA inside The fort tine readings at the "ther emu
and thus permits all the calculations to be maze
IN one spot
Al Fort Monroe il las been found that
target fifteen feet square can be hit every 'ithe
NJ a distance Of nine thousand feet. inc guns
arc proyidcd with graduated scales that tell the
runner how much TO elevate his piece Tor any
particular distance. Hence when the man AT
the range-fnder orce gives him that factor in
his problem all the rest is comparatively easy
work.
One might think that where the base line was
| over a mile long it would be easier to find the
| range than with a much shorter one. But TINS
story is told regarding the first work done al
one OF the forts near this city with the instru-
ment which uses vertical base line. The ON
Ger Of a gun SQUAD was about to indulge In q
little practice. He had figured out the dis
| knce NJ his TARGET the night before BY means OF