Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1917-06-11
OPTICAL INSTRUMENTS IN WARFARE
ny FREDERIC J. HAsKIN

WASHINGTON, June s.-The Fed
Grail Bureau OF Standards. OF the De-
partment OF Commerce, will be ablo
to supply the needs OF the American
army in tho matter Of optical glass.
This Is matter of the very highest
Importance. and represents a distinct
triumph for the bureau In n technical
and scientific way. Tho manufacture
OF high-grade lenses Is one Of the
NEST complex. delicate and difficult
OF the war, the highest degree Of per-
lection in optical glass was attained
only In German and Austrian factories.
1t was part OF tho worlds system
Of scientific production before the war
for cach nation to specialize along
particular lines. Thus, American in
struments OF precision wcre probably
the best made anywhere. In the field
OF optical Instruments. especially OPP
teal glass, Germany and Austria led,
and this leadership gave GerSlany an
immense advantage in the early days
OF the war. But the last three years
have proved that each nation which
makes war must be prepared to sup
ply itself with every essential of war
fare. The Bureau OF Standards has
brought Its work to a point where
America can meet tho exacting re-
quircments OF the army for optical
glass.
The whole system OF modern war
fare may BIO said to be based on the
accuracy OF the results obtained by
tho use OF optical instruments. 1t has
been said that this war goes back TO
the methods OF primitive times-to the
liquid fire of the Greeks and the hand :
to-hand cold steel combats of the days
or chivalry. This is only partly true:
at best. only superficial view of the
question. Basically this war Is a war
or cold science. The infantry charge
Is the elimination OF an artillery fire
from hidden guns shooting at targets
many miles distant which the Kunncrs
cannot see. The accuracy OF this fire
Is based entirely on the accuracy of
observations made by various optical
fundamentally field glasses, range
finders and aeropiane cameras
Nowhere Is the remarkable develop
ment OF finely made glass lenses more
beautifully shown than in the aero
plane camera. These cameras are
literally the eyes OF the army. Every
foot OF the battle ground and the ter
ritory behind 1t Is photographed scores
OF times day. These photographs
are made by men flying 5000 and 10. 900
feet above the ground level at q speed
OF eighty miles an hour or moro, and
they are as clear and distinct as the
cabinet photo OF ten years ago
Lenses Are Closely Calculated.
Only an expert in optical instrumen Is
can appreciate tho triumph of science
represented by the lenses OF these
cameras. A simple lens which will
make photograph Of n sort has no
less than five separate and distinct fac
tors Of error. and would show moth
ing but blur II used under conditions
much less trying than those OF aero
plane photography. In order to over
come the sources OF error, II II ncces-
sary to combine glasses OF different
chemical composition in such a way
that each glass exactly neutraIizes
the error OF the others. The compost
ton of such glasses must be calcu-
lated to the minutest fraction The
glasses must be cooled. nnncalcd.
ground and polished until they are
accurate down to the finest point that
human instruments can measure.
Some Of the great military cameras
In use on the western front make
pictures seventeen inches by twenty.
Such cameras have lenses with what
is known as thirty x-inch focal
length-that liz. the lens Is placed a
yard distant from the sensitive plate.
This IL necessary in order that OBJ
5ccts on the ground may stand out as
large as possible. The longer the dis
lance from lens TO plate. the more
useful arc the photographs from the
military point OF view. But in order
to combine this long focus with speed,
it is necessary for the lens to be very
large. and each increase in size of the
lens increases many times the diff
fculty OF casting and grinding it ac-
curately. The lens on such camera
may be as much as six inches In dia :