New-York tribune., 1902-08-03
INFANTRY RANGE FINDER.
IMPORTANT AID TO MARkSMANSHlP
WITH SMALL ARMS.

An instrument which will enable the soldier to
tell how far away the enemy is at whom he
wants to shoot is a very useful thing. The
elevation of his gun in aiming is controlled by
the distance. In a practice range man knows
what the interval is between himself and the
target and governs himself accordingly But IN
the field, in actual warfare it is pretty much
guesswork. For heavy ordnance, either on snip
board or in coast defences. range finders have
been common for several years. The need OF
apparatus that will perform the same service
for infantry had not been well met uhtlI recent
IL There has been, to be sure, the "mekometer
# the British army. This consists OF piece oI
string fftv feet long and having various de-
vices and u man at each end. But professor
George Forbes an Englishman. thought that he
o,,rd ir,,nroya greatly on it, and tried last year
lie Lot the plltlic know little about 1t early IN
rb.. winter went to South Africa a little later
to try it. and recently he told the United Service
Institution in London the result OF his TASK
The Forbes range finder is much simpler thah
the .'rnekometer" and can be manipulated oS
one man. who is himself shielded from the enc
r,,,,s fira There is light staff or rod six feet
Ions, iojuted in the middle that II can be lo4u
ed I'D when not in use. The rod Is heId hoi'%o'-
tally and at right angles with the direction !"
r.bicn The man is looking-that is. crosswise in
F-gr 81 y
,,hirb catches an image Of the enemy, reflects II
,,, ~. rod to the middle. where another prism
,.,,,ss - a.-ain and sends it into one barrel OF
. lis, field glass There are TWO prlsins at 'i'e
,niddI. Of the rod. Each barrel receives q di-
ferent image"
\ certain amount Of adjustment rs necessary
in order 10 secure Il good. sharp image" mat
adjustment i Effected With "A sor"" having an
enormous fat head which is su"diNlH'' 4N' ii
scale The device is known "s .mi'r"i"''''
s..r.,, % and is commonly attached 10 micro
s,or.s for fine focusing and to telescopes i"T
,,-,suri,7e angles ON thr Forbes rang" hnd'f
~ ,.,,, ,3et-rrliIf.. the distance Of the enemy ry
noting The position Of the m.cr"mrt~r seI""
when he has obtained d perfect focus Near IN"
graduated periphery 4 the screw head is a sta
tionary index with u sharp point, and the mum
hers extend around the entire circle Rotation.
therefore. changes the number opposite the
index.
To assist the eye in focusing, Professor Forbes
nuts into each barrel Of his field glass, where 1t
will not obstruct the Vie" 20" much a trans
parent photograph of a balloon with Il short tan
rope If the centres Of the tvs" barrels are eN-
actly in line with the centres Of the pupils. the
two images VIII coalesce and appear one,
and the balloon will seem to he suspended in
rnidair one photograph can be shifted side
.vays with a micrometer screw. 1t can ho
pushed inward toward the other barrel or with
drawn. This lateral motion makes the balloon
seem to move toward away from the observ-
cr. When the tail rope IS thus made To hang
directly over the column Of troops or the tent
on which the instrument is trained. the focus
is perfect and the scale may he read off. Pro
fcssor Forbes declares that he found it easy to
get within - per cent OF the actual distance by
means of his range finder, when the range was
as great three thousand yards.
A convenient posture for the who uses