The morning news. [volume] (Savannah, Ga.) 1887-1900, 1897-07-04
FINEST LENSES IN THE WORLD.
Description of the 100000 Disks for
YerI0es Telescope.

From the Springfield Republican.
Two pieces OF highly polished glass,
which represent years of patient toll and
a fortune in value, were shipped on a
special parlor car from Clarks' lens works
in Cambridge to Chicago last evening
These disks, which form the lens for the
Yerkes telescope, are the largest ever
made, and with their aid the astronomers
look for most startling discoveries, some
even predicting that the works Of human
bel rs will be detected on Mars. They
were transferred in their cases to the par
lor car In the rear of the lens works at
Cottage Farms Bridge. and the car was
then switched into Boston and attached to
the Chicago express. Prof Alyan G.
Clark, the maker of the lensi Carl A. r.
Luhdin, his foreman, who has spent sew
eral years in polishing the great disks,
and another workman accompany the val
liable cargo.
The Yerkes lens is the largest and finest
in the world. II represents nearly six
years of careful labor and completed is
valued at $4,000 The glass came from
the factory of Mantois, in Paris, France
in May, 1892 and its cost In the rough
work was $40 coo, and for the painstaking
work of grinding and polishing Mr.. Clark
received $4,000, the work taking the larger
part of the Ave years it has been In the
factory at Cambridge. The lens has been
completed and waiting shipment many
months. the delay being due to the fact
that the observatory built by c. T. Yerkes,
the purchaser of the lens, near Lake Gene
va, wis, was not in readiness to receive
it. The lens is Az inches on the surface
diameter and weighs jl5 pounds. The ex-
frfa ar inches
the other inch and a half being taken
up by the casing This makes It just four
inches larger than the Lick telescope lens,
which was also made by the Clarks, and
which has held the place of honor In the
world of astronomy.
This great lens consists of two separate
lenses Of differing density and shape sep
arated when in use by space of several
inches The outer one, which comes in
contact with the atmosphere is made OF
perfect piece of crown glass. 1t
Is double convex, two and three-eight
inches thick at the center and three-quar-
ters of an inch at the edge, and weighs
POS pounds The inner tense is made Of
flint glass. and is what Is known as piano
concave. 1t is enc and one-eighth inches
IN thickness at the center and two inches
at the edge. II weighs $40 pounds. Both
lenses are adjusted In an iron ring and
cell. and the total weight of the glass and
distance OF the lens Is slxty-one feet
The packing OF the lenses was one Of
the most interesting features In their his
tory, and IL was completed Saturday.
First, they were carefully and smoothly
wrapped in flannel sewed tightly on the
edges Then they were covered with sew
eral thicknesses Of soft tissue paper. and
then wrapped In hard paper, and incased
In a bed OF cotton batting, silk aud curled
hair in a strong, yet handsomely finished
box. This box was mounted upon springs,
and placed within larger box and packed
excelsior. The springs within the outer
casing, between that and the innor box.
are designed TO detract from any Jar that
the outer case may sustain and thus save
the lens from the effects OF almost any
shock.
The great glass disks OF these lenses
were cast I'm Paris. and a year was taken
In preparing the material and casting a
dozen or more before a perfect one was
secured. Even then II had 70 be cut and
recut before all the air bubbles and IN
equalities were carved out Of a.. When
they arrived at the Clarks' works they
were rough and crude, with very little
shape 10 them. The care, the skin, the
patience which have been expended IN
grinding the lenses Is marvellous. There
Is little machinery about II and no Sc
crets And yet there are few men IN the
world who have earned "A reputation like
the Clarks, or whom there Is only one left,
Prof. Avian O., the maker Of the largest
lenses In the world The icnsemakers
art Is well-nigh the highest form OF hand
icraft, ana patience Is tho main factor 10
success. When the glass was received Il
was FIRST tested for trial. II was set on
edge midway OF a long, dark room, with
Hight at ono end, and the examiner at
the other. An assistant held a lens be-
tween the light and the disk, and the
rays as they we're intensified upon the
disk magnihed any imperfections. The
glass was next tested for poiarlzed light.
being viewed In the outer light through a
revolving nicol prism Having stood these
tests the glass was ready 60 Sc shaped
The two essential things nj the outset In
making a telescope lens are the specin-
cations OF the diameter and length OF To-
Gus. The problem IL to determine what
curve % give the glass IN order that every
ray Of llght which strikes the specified
surface may be refraeted TO a common