New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1899-04-09
>r,,,u vop11 TRIRJ1NE ILLUSTRATED SUPPLEMENT-

NIGHT - is necessary to secure illumination by
making tbe objective. or lens at the big end,
very wide.
The most marked advances that have been
made in recent years, as represented by what
are known ms the Zeiss and Goerz glasses are In
the increased magnihcation and enlarged ield
obtained with n small instrument These glasses
also have another notable virtue, to which rel
erence will be made in moment. But some OF
them, although no longer than common opera
glass will develop power OF from SIX 10 nine
diametcrs Even the twelve power glass is not
much bigger than the ordinary opera glass. The
great rnagnifcation here indicated Is secured by
using an eyepece like that Of an Astronomical
telescope: but inasmuch as the telescope inverts
its image it was necessary to find way to
turn the picture right side up again
The means employed for this purpose accom-
plsh another object at the same time. The OBJ
iect glasses of the new instrument are about two
inches further apart than those Of the ordinary
opera glass. The two lines Of sight are bent four
times by the of the rejecting surfaces OF
prisms, so that when they eventually pass
through the eye lens they are once more paral-
lei to each other but closer together. In this
manner a stereoscopic effect IS secured. which
adds much to the vivldness Of the scene In
passing it may be remarked that as long ago
the Civil War I'm this country Charles Lembkc.
the we'll known Union Square optican, made
glasses for army use in which prsms were en-
poyed His arrangement of them was different
from that Of the newer instruments. but they
performed their work satisfactorily.
In order to obtain the best results with an
otherwise good instrument it is desirable that
the central line Of each barrel shall coincide with
the centre Of the pupil of one eye. But the dis
lance between the eyes is greater in some per-
sons than in others Consequently. some high
grade glasses notably binoculars are so con-
structed that the two barrels can be moved
apart or closer together In the Zeiss glass this
adjustment is made by bending the two halves
upon hinge like that of a door. In the Goerz
there is a ratchet. such is used for focusing
You can focus each barrel separately in the
Zeiss glass. There is often enough difference be-
tween the two eyes Of person to make this
feature 4 distinct advantage. In the GOcrz glass.
after having made an adjustment for such a diff
ference. the two barrels can be controlled stimuli
taneously with single thumbscrew.
THE QUESTION OF COST
or course. the modern improvements cost some
thing. One can get a pretty decent opera glass
of the old style. maynifying two diameters and
free from serious defects for between So and $40
nine power binocular, such as is used In Uncle
Sans lighthouses, can be had for $50 or there
abouts. nine-power glass of the prismatic
and stcreOscopc type costs between $50 and $50
For about so one fine instrument
of the latter class for field use. magnlfyng six
damcters. and for $40 or $50 4 twelve power
glass.
In conclusion. bit of advice may be of
fercd. 1t is safer. when wishes to buy an
opera field glass. to go to a well-known
optician who understands his business. and who
will help a customer find what is wanted, rather
than patronize a dealer who handles large
variety of other goods as we'll and puts mex
perenced statesmen in charge of his optical
wares.